Succulent boneless leg of lamb is slow roasted with garlic, citrus and rosemary. Make this recipe using boneless or bone-in leg of lamb.
Is lamb meat from baby sheep?
Many people associate the word lamb with baby sheep. As a result, it is likely one reason that some shy away from eating it.
The truth is, lamb are sent to slaughter between 6 and 8 months of age. While young, sheep of that age are not babies.
At the age of slaughter, those young sheep weigh close to 100 pounds!
The industry uses the term lamb to define the meat of any sheep under one year of age. After one year, they are known as mutton.
Lamb meat is more tender than mutton, which is why a leg of lamb roast is the popular choice!
Ingredients for boneless leg of lamb
The ingredients to make roasted lamb are pretty straightforward. Aside from the lamb meat, all you need are:
- Onions – White or yellow, whichever you prefer
- Celery – The celery is for flavor only. Because you won’t be eating it, you can even use the leafy tops of the stalks.
- Carrots (To save on prep time, I like to use baby carrots)
- Garlic – Using fresh cloves of garlic provides the best flavor
- Oranges – The citrus juice lends a fantastic sweetness to the roast leg of lamb. For an especially sweet citrus flavor, you can use Mandarin oranges.
Lamb roast: bone-in or boneless?
There are two types of lamb roast; using a bone-in or boneless leg of lamb. The recipe card below explains how to make both types. I’m basing the instructions here on a bone-in roast, which is what I use.
Any time you cook meat in the oven, using a bone-in roast is the way to go. Not only is it more delicious, but also, the meat stays juicier.
The bones lend a lot of flavor to the lamb meat in this recipe.
How to make pan gravy
When the leg of lamb finishes cooking, remove the roasting pan with the lamb from the oven. Transfer the lamb meat to a cutting board or serving platter. Tent it with foil and allow it to rest while you prepare the pan gravy.
- Move roasting pan to stove top over 2 burners. If it won’t fit over two burners, you can transfer the contents to a skillet.
- Using a slotted spoon remove the vegetables (See Recipe Card Note), rosemary sprigs and citrus, leaving the roasted garlic.
- Mash the garlic with the back of a wooden spoon and bring the pan juices to a boil. Sprinkle the flour over the gravy and whisk to incorporate. Turn heat to low and simmer until thickened.
- If the gravy is too thick, add a tablespoon of water to thin it out. Or, to thicken it, cook longer to reduce the contents.
- Feel free to strain if you do not want the garlic/rosemary pieces in your gravy. Instead, place them alongside the roast leg of lamb.
Also, consider serving a vegetable like spring peas, roasted Brussels sprouts, or creamed spinach.
Video: How to oven roast boneless leg of lamb
Want to see the recipe in action from start to finish? Just watch the video below!
Bone-In or Boneless Leg of Lamb + Video
- 5 1/2 lb leg of lamb (bone in) (For boneless, See Note 1)
- black pepper
- 1 large onion quartered
- 1 large orange quartered
- 2 ribs celery
- 2 cups cut carrots
- 1 large head of garlic (about 15-20 cloves)
- 3-4 fresh rosemary sprigs (6+ inches long)
- 4 cups beef broth
- 2 cups water
- 2 tbsp olive oil
- 1/4 cup flour
- Preheat oven to 300°F.
- Cut and quarter the onion and orange. Break up the head of garlic and remove skins or have 15-20 cloves peeled and ready. Rough chop the celery and set all in the bottom of a large roasting pan with the carrots and rosemary.
- Lay the leg of lamb on top and season generously with kosher salt and black pepper on both sides. Leave the bone side up and pour in the beef broth and water. Drizzle the olive oil on top of lamb and then cover with aluminum foil and place in the hot oven for 5 hours (See Note 2 for different weights and roasting times).
- Remove from oven and set aluminum foil aside. Carefully flip leg of lamb, baste with pan juices and return to oven to roast, uncovered for 45 minutes or until the outside is a rich, golden brown.
- Remove lamb from pan and keep warm on a serving plate with the aluminum foil covering.
For Pan Gravy
- Move roasting pan to stove top over 2 burners. Using a slotted spoon remove the vegetables (See Note 3), rosemary sprigs and citrus, leaving the roasted garlic. Mash the garlic with the back of a wooden spoon and bring the pan juices to a boil. Sprinkle the flour over the gravy and whisk to incorporate. Turn heat to low and simmer until thickened. Add water if too thick, or cook longer to reduce if gravy is thin. Feel free to strain if you do not want the garlic/rosemary pieces and serve alongside roasted leg of lamb. I serve with mashed potatoes.
- Medium Rare (internal temp should be 145°F) 20 minutes per pound
- Medium (internal temp should be 160°F) 25 minutes per pound
- Well Done (internal temp should be 170°F) 30 minutes per pound
- 4 to 4.5 pound leg of lamb roast covered for 4.5 hours and uncovered for another 45 minutes or until the outside is a rich, golden brown.
- 6 to 6.5 pounds, roast covered for 5.5 hours and uncovered for another 45 minutes or until the outside is a rich, golden brown.
The information shown is an estimate provided by an online nutrition calculator. It should not be considered a substitute for a professional nutritionist’s advice.