This slow-roasted boneless leg of lamb is roasted for 4 hours on a bed of vegetables. It's tender, easy to make, and serves a decent-sized crowd. This slow-roasted leg of lamb is made similar to slow-roasted lamb shanks in foil packets, however, everything is combined into one baking dish. Both recipes make a delicious, tender lamb infused with fresh garlic and herbs.
What I Love About This Recipe
I love that this one-pan meal has the starchy potatoes, carrots, celery, and boneless lamb leg all slow-roasting together. The flavor is incredible, the lamb is very tender, and this recipe serves a good-sized crowd. You can choose to make the lamb gravy or not, it's completely optional.
- Chopped vegetables: I use celery, carrots, potatoes, and onion, however, other vegetables can be substituted. I recommend fibrous vegetables with long cook times for this low and slow lamb roast recipe.
- Boneless leg of lamb: I use the boneless leg of lamb roast (from Costco) thats about 4 to 5 lbs (around 2.2 kg). Substitute a similar sized bone-in leg of lamb for the boneless leg of lamb if desired.
See the recipe card at the bottom of the post for quantities.
How To Make Roasted Boneless Leg of Lamb
Set the oven to 325 ℉ (165 ℃). Peel and chop the carrots, potatoes, and onion. Wash and chop the carrots. Add chopped vegetables to the baking pan.
Keep the mesh string on the lamb roast to keep it together. Marinate the lamb with mashed garlic, lemon juice, and a dried Italian herb blend. Place the lamb roast on top of the bed of vegetables.
Add a layer of parchment paper and then tightly wrap with foil.
Bake at 325 ℉ (165 ℃) for 4 hours completely covered the entire time with foil. After 4 hours, pull out of the oven and remove the parchment paper and foil.
Set the oven to broil. Uncover the lamb and broil for about 3 to 5 minutes, or until the top of the lamb crusts.
Pro Tip: I recommend removing the mesh string prior to broiling (unlike the photos) so that the seasoning doesn't stick to the string.
Either serve the roasted boneless leg of lamb as is or prepare a lamb gravy using the leftover lamb drippings.
Pro Tip: Slice the lamb just before serving so the meat doesn't dry out.
How To Make Lamb Gravy
To make the lamb gravy, separate the lamb and vegetables from the juice using a slotted spoon. Pour the lamb drippings through a mesh strainer to remove any large chunks still remaining. Set the lamb drippings aside.
In a small pot on the stovetop, add 2 tablespoons of butter on high heat. Once the butter is melted, add 2 tablespoons of flour. Whisk the butter and flour together for about 30 seconds or until fully combined. Add the strained lamb drippings (about 2 cups) continuing to mix together with a whisk. Remove from the heat once the lamb gravy thickens after about 1 minute.
Serve the lamb gravy on the side. Slice the lamb so it's easy to serve.
Tips and Tricks
- Marinate the lamb ahead of time. Add the mashed garlic and lemon juice to the lamb about 2 to 4 hours prior to roasting.
- Don't use any fat. Lamb naturally contains a high fat content, so added butter or olive oil is not necessary.
- Chop the vegetables in large chunks. The vegetables cook for a long time, so larger size chunks hold up better.
- Use fresh garlic. I highly recommend using fresh garlic and mashing it with a mortar and pestle for seasoning the outside of the boneless leg of lamb.
Variations and Substitutions
- Use a bone-in lamb leg. If you would prefer a bone-in lamb leg, use one! Just make sure the bone-in lamb leg is about the same size, so the temperature and cooking times will be the same.
- Season with fresh herbs. Substitute fresh herbs for dried herbs.
- Use a different combination of dried herbs or no dried herbs at all.
- Peeler for peeling the potatoes and carrots
- Chef's knife and cutting board for chopping the vegetables
- Mortar and pestle or garlic press for mashing the fresh garlic cloves
- Lemon squeezer for juicing the lemon
- 9" x 13" baking dish to roast the boneless leg of lamb
- Parchment paper and foil to tightly cover the lamb as it bakes in the oven
- Small stovetop pot for making the lamb gravy
- Whisk for whisking the lamb gravy
Store the lamb and roasted vegetables in an airtight container in the fridge for up to 4 days.
Both types of lamb have pros and cons. A bone-in leg of lamb roasts with the bone, creating a very flavorful roast. The leftover lamb bone can be used for bone broth also. A boneless leg of lamb is easy to carve but lacks the added flavor of the bone roasting with the lamb roast.
When comparing two lamb leg roasts of the same weight, a bone-in leg of lamb cooks slightly slower than a boneless leg of lamb. If roasting the lamb leg at a low temperature for a long time, the roasting time is pretty much the same.