Roasted Leg of Lamb

Rubbed with a delicious fresh herb mixture and roasted to perfection using the step-by-step method below, this lamb comes out incredibly tender, juicy, and flavorful.

An Easy Method to Make Tender Meat

The leg of lamb recipe below uses a reverse sear technique which is easy, all you need is a meat thermometer.

Often meat is seared at a high temperature to get a crust and then cooked at a lower temperature to finish it. To reverse sear (like below), the meat is cooked at a low temperature first and then browned/seared at the end.

The lamb roast will go in the oven and cook at a low temp and then be removed from the oven. At the end of cooking,  the oven is turned up high to make a crust or “sear” the outside of the lamb.

I use this technique with Roast Beef Tenderloin as well because it makes an incredibly tender roast with a more even cooking throughout the meat.

Ingredients for Roasted Leg of Lamb

For this recipe, you’ll need a leg of lamb of course, and some fresh herbs with seasonings to make the rub and add great flavor.

Seasoning Rub: This rub is a combination of fresh herbs, garlic, and a bit of dijon or grainy mustard. They can be finely chopped or pulsed in a mini food processor. Be sure to use Kosher salt, if substituting table salt, reduce the amount.

You can add other herbs or even lemon zest to your liking.

What Kind of Lamb to Buy

This recipe is for a boneless leg of lamb.

A leg of lamb is a leaner cut than a lamb shoulder. The shoulder is more fatty, similar to a pork shoulder used for pulled pork.

The boneless lamb in this recipe is a leg of lamb where the bone has been removed and it is rolled and tied into a roast. I like it because it is lean and cooks evenly. Being boneless makes it easy to cut for beautiful slices.

I have not tested this recipe with other cuts of lamb including a bone-in leg of lamb.

How to Roast a Leg of Lamb

The leg of lamb recipe below uses a reverse sear technique meaning it is cooked at a low temperature and then at the end, the temperature is increased to brown the outside. It cooks evenly and is very very tender when prepared this way.

You will need a meat thermometer or instant read thermometer for this recipe.

1. Season the lamb roast with the rub per the recipe below.
2. Place it in a roasting pan and slow cook it in a low oven to 115°F.
3. Remove it from the oven for 15 minutes and turn the temperature up high.
4. Roast until the lamb reaches medium-rare per the recipe below (about 20 minutes).
5. Rest before slicing with a sharp knife.

I find a lean leg of lamb doesn’t have enough juices for gravy, so we serve it with our favorite mint sauce and garnished with roasted onions.

How Long to Roast Lamb

For this reverse sear method, the lamb will roast to 115°F first and then finish off at a higher temperature.

A 3-4lb roast will take about 60-80 minutes to reach 115°F and then will rest for 20 minutes and finally cook an additional 20 minutes. The total cooking time will be about 1 ½ hrs to 2 hours.

• The cooking times are for lamb that has been removed from the fridge at least 60 minutes before cooking.
• If the lamb is browned and hasn’t reached the desired temperature, turn the oven off and it will continue to cook.
• If the lamb is done early, before you’re ready to serve it, it can rest longer before cutting.
• These cooking times are an estimate for a boneless lamb roast. Times can vary based on the shape of the roast, the type of pan used, and other factors, this recipe relies on a thermometer.

Lamb Temperatures

Ensure the lamb reaches the internal temp as indicated below (after resting).

Medium Rare 135°F Dark pink center
Medium 145°F Pink center
Medium Well 155°F Browned center with very little pink

Important Tips for This Recipe

• Remove the lamb from the refrigerator at least 60 minutes before roasting to bring it to room temperature before cooking.
• Use a meat thermometer for this recipe.
• Reverse sear can cause some smoking if there is a lot of fat in the pan. To reduce smoking, move the lamb to a clean pan before searing at a higher temperature.
• Remove the lamb from the oven about 7-10 degrees before your desired doneness. The lamb will continue to rise in temperature about 10 degrees as it rests.
• The lamb must rest at least 10 minutes (I usually allow 20 if time allows) before slicing.
• Cut across the grain.

Recipe Ingredients

• 1 boneless leg of lamb 3 to 4 pounds
• 2 tablespoons olive oil
• 2 cloves garlic minced
• 2 tablespoons fresh parsley
• 1 tablespoon fresh rosemary
• 1 tablespoon grainy mustard
• ½ tablespoon fresh thyme
• ½ tablespoon kosher salt more to taste
• ¼ teaspoon fresh black pepper

For Serving

• fresh parsley for garnish
• mint sauce optional but recommended

Recipe Instructions

1. Remove the lamb leg from the fridge at least 60 minutes before cooking.
2. Preheat oven to 250°F.
3. Chop the herbs and combine them with the herb rub ingredients in a small bowl.
4. Dab the lamb dry with paper towels. Rub the lamb with the herb rub.
5. Place in a rimmed baking pan and bake until internal temperature reaches 110-115°F, about 60-80 minutes depending on size and shape.
6. Remove from the oven and rest 20 minutes. While the lamb roast is resting, turn the oven up to 475°F.
7. Place the lamb roast on a clean pan back into the oven and cook until it reaches 125-130°F (or as desired per the temperatures below), about 15-20 minutes. *See note. The temperature will increase about 10°F while resting.
8. Rest 10-15 minutes before cutting and serving.

Recipe Notes

A meat thermometer is essential for this recipe. Cooking times can vary based on the type of pan and the shape/size of the roast.

Allow the lamb come to room temperature before roasting.

Remove the lamb from the oven at 110-115°F for the first cook. When you turn the oven up to a high temperature the lamb will become get a browned crust.

The second cook is at a very high temperature to form a nice crust so you may experience some smoking in the oven due to the oil and juices in the pan. To reduce smoking, transfer the lamb roast to a clean pan. If the lamb has a browned crust to your liking but hasn’t reached 125°F yet, you can turn the oven off and leave it in the oven until it reaches the desired temperature.

Be sure to rest before cutting.

Do not overcook. The lamb leg will continue to rise 5-10°F as it rests so be sure to take it out early.

Medium Rare 135°F Dark pink center

Medium 145°F Pink center

Medium Well 155°F Browned center with very little pink