The Food Lab's Definitive Guide to Buying and Cooking Leg of Lamb

J. Kenji López-Alt

Thu, December 11, 2014 at 1:30 PM UTC

19 min read

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Everything you need to know about purchasing, seasoning, and cooking leg of lamb.

<p>Serious Eats /  J. Kenji López-Alt</p> Tender and flavor-packed boneless leg of lamb with a crisp crust. — Serious Eats / J. Kenji López-Alt
Tender and flavor-packed boneless leg of lamb with a crisp crust.

It always baffles me when I hear statistics about lamb consumption in the US. Compared to chicken, beef, and pork sales, lamb consumption is a drop in the bucket—two full orders of magnitude lower than chicken consumption. For every 100 pounds of chicken eaten by the average American, we consume less than a single pound of lamb!

And why? It's certainly one of the most delicious meats around, with its, er, meaty texture, and intense flavor. Is it availability? Probably not. Lack of exposure? Maybe. Or is it just that it's often not cooked very well, resulting in an overly gamey flavor and dry texture?

My bet's on the latter, and because I love lamb so hard, I'm going to try my best to remedy that situation, starting with the best way to cook a boneless leg of lamb. I'm talking about a method that delivers mild, flavorful meat with a tender texture and a perfectly rosy medium-rare hue all the way from edge to center, surrounded in a crisp layer of browned, crackly fat.

Here's my guide to getting it there.

The Quick Version

Our quick and dirty recommendations if you want to jump straight into the kitchen.

Buy a butterflied boneless leg of lamb (American if you prefer it milder in flavor, New Zealand or Australian for stronger). Rub it with some intense aromatics like garlic, rosemary, and lemon zest. Roll and tie it. Roast it in a rack in a 275°F (135°C) oven until it hits 125° to 130°F (52 to 54°C) for medium rare, about three and a half hours. Remove from the oven and rest for 30 minutes while you increase the oven temperature to 500°F (260°C). Return it to the oven for 15 minutes to brown. Remove the twine, carve, and serve.

Why Lamb?

You heard right: We eat over 100 pounds of chicken per year each, but when it comes to lamb, we eat only 0.8 pounds per year, and the amount is getting smaller every year—back in the 1970s, it was at a larger, but still woefully tiny, three pounds per year. Not only that, but the vast majority of Americans don't eat a single bite of lamb all year. Most of this per capita consumption comes from minority communities—Greeks, Muslims, Indians—who eat a ton of it, bringing up the entire average.

Even more dire is the fact that lamb is what economists call an "inferior product," which means that its demand is inversely proportional to average consumer income. When people have money to spend, they'd rather spend it on beef and chicken breasts. A 2001 study from Kennesaw State University in Georgia found that for every 1% increase in consumer income, there was a corresponding 0.54% decrease in lamb consumption.

It's an odd dichotomy, because while in many communities, lamb is seen as the "cheap" meat—the meat to buy when you can't afford beef—in high-end food and fancy supermarket circles, it's often far more expensive—and desirable—than beef.

I'm with the latter camp. I can think of precious few situations when I'd rather have a steak than a fatty, musky lamb chop. Or when I'd rather have a pot roast than a rich, slightly funky braised lamb shank. And when it comes to holiday roasts, the prime rib may be the king of the table, but the roasted leg of lamb is his wilder, funner cousin.

Shopping: Domestic vs. Imported Lamb

Q: I see lamb from Australia, New Zealand, and the U.S. at the butcher. What are the differences between these options, and is one better than another?

There are major differences both in terms of flavor, size, and price when it comes to American lamb vs. lamb from Down Under.

New Zealand/Australian lamb are quite small in size, with whole legs coming in at around five to six pounds. According to Mark Pastore of Pat LaFrieda Meats, it's a matter of both genetics and feed. Lambs from that area are smaller to begin with, and they spend their entire time grazing on grass, giving them a more intensely gamy flavor that some people can find off-putting. They also tend to be lower in fat, making them a bit harder to cook properly—legs in particular have a tendency to dry out. That said, if you're cooking for a smaller party—6 to 8 people or so—and you value gamy flavor over tenderness or richness, NZ or Aussie lamb is a good choice.
American lamb, on the other hand, are larger, fattier, and sweeter in flavor. Most American lamb are fed on grass most of their lives which gets supplemented with grain for the last 30 days before slaughter. The lamb at LaFrieda comes from Mennonite farms in Colorado that finish their lamb on a combination of grain, honey, alfalfa, wheat, and flaked corn. The results mean a much larger layer of protective fat around the legs, as well as better marbling. The lamb bastes itself as it cooks, helping it to maintain a moister, more tender texture. Because of the grain supplements, American lamb tends to also have a less funky, richer favor. A single leg of American lamb can weigh up to 15 pounds or so, with enough meat to feed over a dozen.

Q: I've read that grass-fed meat is always better—better tasting, better for the animal—is there any truth in this?

It depends on your point of view. Some people do prefer the gamier taste of 100% grass-fed lamb, while others prefer the richer flavor and juicier meat in grain-finished lamb. As far as the health of the animal goes, while it's true that an animal that lives solely on grain would eventually develop health problems (much like a human who exists solely on hamburgers), grain finishing only takes place for the last 30 days of a lamb's life, after which it's going to be slaughtered anyway. This time period is not nearly long enough for the animal to develop any health problems that would cause it to suffer in any way.

In fact, given the choice between grass and grain, sheep (and cows, for that matter), choose grain every single time. Finishing sheep on grain is as simple as providing grain to feed on in their fields. They could still eat grass if they wanted to, but they choose not to.

Q: And what about the price differences?

Unfortunately, American lamb tends to be more expensive than imported lamb, despite their long journey across the globe. It's a matter of scale. Australia and New Zealand's lamb output is several times greater than that of the U.S. If you value tenderness and juiciness, the extra cost is probably worth it.

Q: How much lamb should I buy?

Plan on buying 1/3 of a pound of boneless lamb per person, or 1/2 to 2/3 of a pound of bone-in lamb.

Bone-in, Boneless, and Butterflied: What's the Difference?

Bone-in leg of lamb comes in two forms: shank end, and sirloin end (occasionally, you'll find a massive one for sale with both the shank and the sirloin still attached). The shank end lamb legs start at just above the lamb's ankle and go to midway through the calf bone, while the sirloin-end legs start at the hip and stop at around the knee.

I prefer the sirloin end because the meat is fattier, more tender, and the cut is more evenly shaped, making it easier to cook evenly. On the other hand, the shank end tends to have slightly more flavorful meat. Its tapering shape is desirable for some cooks, who like being able to offer both medium-rare meat from the thick upper part and well-done meat from the thin lower part all off of the same roast.

Because the bone acts as an insulator, boneless lamb leg cooks faster than bone-in lamb leg, giving you more leeway in terms of hitting the exact doneness you want, but this advantage can be easily mitigated with careful monitoring and a good thermometer.

Boneless leg of lamb often comes sold in netting in order to help keep its shape during cooking. It offers several advantages to bone-in lamb. First of all, it's lighter, making the arduous task of lifting it in and out of the oven much easier on the back. It's also easier to calculate how much you need to feed your party. Finally—and this is probably the greatest advantage of all—it's far easier to carve—just cut straight through it into neat, even slices.

<p>Serious Eats / J. Kenji López-Alt</p> — Serious Eats / J. Kenji López-Alt

Butterflied leg of lamb is a boneless leg of lamb that has been split open and rolled out. This is how I prefer to purchase my lamb; it affords me opportunities to season it both inside and out. Often this just means a quick rub with salt and pepper before rolling it up and tying it, but often it can mean more elaborate rubs or herb mixtures. If you choose to go with a butterflied leg, you'll need to know how to tie it up before roasting.

How to Prep and Season Boneless Leg of Lamb

Q: Leg of lamb can be very gamey. How can I make its flavor a little milder?

But here's the thing: Most of the compounds that give lamb—or any meat—its distinct flavor tends to be concentrated in its fat. In fact, if you grind lamb fat into a lean beef hamburger or cook a lean beef steak in rendered lamb fat, you'd swear that you were eating lamb. The lesson? Minimize the fat and you minimize the gaminess. By boning out the leg and butterflying it, you get a chance to remove the large pockets of fat (which tend to be localized around a few major intermuscular glands), thereby reducing its gaminess while also making the lamb easier to carve and more pleasant to eat. Exterior crisp fat can be great, but too much soft, greasy interior fat can be excessive, even for a fat lover like myself.

If you ask your butcher to bone out a lamb leg for you (or better yet, just buy it pre-boned), it's short work to reduce the remaining excess fat in there. To do it, work your fingers in between the individual muscle groups (It should be easy to feel where the seams are), locating the pockets of hard fat in and among them. Use the tip of a sharp boning or chef's knife to trim it away, leaving the fat around the exterior of the leg.

Q: What are some good flavoring options for butterflied lamb?

Salt is a must, and just like with steak or a beef roast, the best time to salt your meat is at least 45 minutes before you start cooking it, and even up to overnight if possible (keep it in the fridge uncovered). This gives enough time for the salt to draw out the liquid, dissolve, then re-enter the meat, seasoning it better than if it were just stuck to the surface.

With its robust flavor, lamb takes well to all kinds of spice mixes and aromatics without allowing them to overpower the meat. With a butterflied leg, you want to apply your seasoning to both the inner and outer surfaces before rolling the thing up. Here are a few of my favorite combinations:

Lots of garlic and oregano or rosemary. Roughly chop a dozen cloves of garlic and a few tablespoons of fresh oregano or rosemary leaves in a food processor, then mix it together with a quarter cup of olive oil. Season to taste with plenty of salt and pepper.
Olives and parsley. Place a cup of good pungent olives like Taggiasche or high-quality kalamata in the food processor along with a cup of fresh parsley leaves and a few tablespoons of olive oil. Pulse until nearly puréed, then spread the paste all over the inside of the lamb. If you want to get extra pungent, add a half dozen anchovies to the mix as well. You should go easy on the salt because of the salty olives.
Five-spice. Chinese five-spice powder with cinnamon, fennel, star anise, Sichuan peppercorn, and cloves provide an interestingly sweet/hot/pungent flavor profile to the meat. I like to add a touch of sugar, soy sauce, and oil to the mix as well to more deeply flavor the meat.
Harissa. This spicy North African condiment has a particular affinity for lamb with its heat, vegetal notes, and warm spice background.
Ras el Hanout. Another North African flavor combination, it's a dry rub that includes cardamom, clove, chile, coriander, pepper, cinnamon, and occasionally floral herbs like lavender or rosehips. You can buy it in specialty spice stores, blend it yourself, or order it online.

Want a more specific suggestion and instructions? This slow-roasted boneless leg of lamb with garlic, rosemary, and lemon is a great place to start.

Q: Why should I tie up my butterflied lamb leg?

A bone-in leg of lamb resembles a cone, with a very thin tapered end and a fat end. Because of this, cooking it evenly is a nearly impossible task: The meat on the thinner end is inevitably going to cook more than the meat on the fat end. This is fine if you've got an uncle or a strange cousin-type thing who enjoys dry, gray meat—heck, it even lets you question their life choices, making for great family dinner table conversation—but assuming that rare to medium meat is on everybody's agenda, a more or less cylindrical shape is what you're after. Tying helps lamb retain this shape as it cooks.

Long story short: If you don't tie up your lamb leg, it won't keep a regular shape during cooking. Irregular shapes lead to uneven cooking. Uneven cooking leads to unhappy bellies. Unhappy bellies lead to lack of familial harmony, and familial disharmony leads to ruined holidays. Would you risk ruining a holiday for five minutes and the cost of a roll of butcher's twine?

Q: How do I roll and tie up a butterflied leg of lamb to prepare it for roasting?

Simple. After laying your lamb out flat and seasoning it, roll it up again with the fat on the exterior, then lay it seam-side-down across pieces of butcher's twine that you've already thoughtfully laid out in parallel lines on the cutting board at one-inch intervals, each piece long enough to tie easily around the roast. Working from the outside towards the center, tie up the lamb. You can show off by using fancy self-cinching butcher's knots, but regular old granny knots (the kind you tie your shoes with) will do just fine.

Your lamb is now ready to cook.

Cooking and Carving Leg of Lamb

Q: What's the best way to roast a leg of lamb?

Just like with cooking any large piece of meat, you've got a decision to make right off the bat: Do you want to cook hot, or do you want to cook cool? Cooking in a high oven will obviously get dinner on the table much faster, but it'll also lead to much more uneven cooking, with the outer layers of the meat overcooking and turning gray by the time the very center is done. Now, I understand that some people don't mind this. I like having some medium-rare juicy meat and some tougher well-done meat on my plate, they say. Those of you who feel this way should be thankful—it makes cooking roasts very easy. Just bang it in a hot oven (around 400°F or 205°C should do), and roast until the very center reaches the desired temperature.

On the other hand, if you, like me, want your lamb evenly cooked from edge to center, the best thing to do is slow-roast it. Just as when cooking prime rib, the best way to do this is to first place it on a rack in a 200°F (95°C) oven until it's within a few degrees of your desired serving temperature (use that thermometer!). After removing it, crank the oven up as far as it will go, then throw the lamb back in for about 15 minutes before serving in order to crisp up the well-rendered fat layer on the exterior.

Q: How do I know when my leg of lamb is done?

First things first: Ignore any and every timing chart you've ever seen—they don't work because they don't take into account basic things like shape and fat content, both of which can drastically affect how fast your meat cooks. Instead, get yourself a good instant-read digital thermometer.

Doneness levels for lamb are pretty much the same as for beef:

120°F or 49°C (rare): Bright red and slippery on the interior. Abundant intramuscular fat has yet to soften and render.
130°F or 54°C (medium-rare): The meat has begun to turn pink, and is significantly firmer, juicier, moister, and more tender than either rare or medium meat.
140°F or 60°C (medium): Solid rosy pink, and quite firm to the touch. Still moist, but verging on dry. Fat is fully rendered at this stage, delivering plenty of flavor.
150°F or 66°C (medium-well): Pink, but verging on gray. Moisture level drops precipitously, Chewy, fibrous texture. Fat has fully rendered, and has begun to collect outside the steak, carrying away flavor with it.
160°F or 71°C (well-done): Dry, gray, and lifeless. Moisture loss is up to 18%, and fat is completely rendered. What was once lamb is now dust.

And just like with beef, I personally recommend cooking to at least medium rare—it's hot enough that the abundant fat in the meat begins to melt, lubricating and flavoring the meat. Rare lamb is tougher and less flavorful.

Q: Can I cook my lamb sous-vide?

Yes, absolutely. It's one of the best ways to do it. Season your lamb and seal it in a large vacuum bag, then drop it into a water bath at your desired finished temperature (I go for around 140°F/60°C). Since the lamb is so large, it'll take some time to heat through to the center, so you'll want to give this at least eight hours and up to around 12. Any longer than that, and the meat will begin to turn mushy from the accelerated enzymatic breakdown of muscle fibers. Nobody likes mushy lamb.

Once you've finished cooking it in the water bath, remove it from its bagging, dry it with paper towels, then finish it off just like you would a slow-roasted piece of lamb by banging it in a screaming hot oven for 15 minutes to crisp up the fat.

The meat you end up with is awesomely tender, moist, and perfectly cooked.

Q: Do I need to let my lamb rest before carving?

You've been paying attention. Just like with a steak, lamb muscles tighten when they're hot. As they loosen up, their ability to retain their juices increases. This means that more juice ends up in your meat, and less on the cutting board. Allow lamb roasted at high temperatures to rest for at least 20 minutes after removing it from the oven, and meat roasted low and slow to rest for at least 10.

Q: What's this "carryover cooking" I hear about?

Carryover cooking is the phenomenon that occurs when you remove a hot piece of meat from the oven. If you cooked it in a very hot (350°F or 175°C+) oven, the center of the meat may be at, say 110°F (43°C), while the outer layers could be as high as 170° to 180°F (77 to 82°C). As the meat rests, some of the heat energy from the outer layers is transferred to the center, causing it to continue to rise in temperature even after the beef is removed from the oven.

When roasting a large piece of meat from start to finish in a hot (350°F+/175°C+) oven it's important to remove it a good 15°F lower than you want to serve it at. Meats roasted at low temperatures—say, 250°F (120°C) or lower—will experience very little carryover cooking, as they tend to cook more evenly from edge to center.

Finishing a roast by blasting it in a 500°F+ (260°C) oven for a few minutes to crisp the exterior will not cause any carryover cooking.

Q: How do I carve a leg of lamb?

Carving a boneless leg of lamb is as simple as removing the twine and slicing it into 1/4-inch slices. A bone-in leg of lamb is a little more difficult.

When you've got a bone-in leg of lamb, you'll notice that the bone runs along one side of the bulk of the meat. You want to slice from the opposite side. Using a fork or tongs to hold the lamb steady, use a long, thin carving knife to separate the meat into thin slices. Some of these slices may remain attached to the bone, but that's ok. Separate them by then making a single slice across the top and side of the bone. The slices should fall away neatly for you to serve.

Storing and Serving Leftovers

Q: I purchased a large leg of lamb and ended up with way too much meat. What should I do with it?

As with prime rib, it's easiest to store leftover roast lamb as one big chunk rather than individual slices, so make sure you slice your lamb to order instead of slicing the whole thing ahead of time. The best way to reheat it is the same way you cooked it: in a low oven until it reaches the desired internal temperature. Smaller pieces work well in a low-powered microwave as well.