This succulent, flavorful roasted boneless leg of lamb recipe is bound to be the star of your holiday dinner table. Serve it alongside roasted potatoes with mint chimichurri for a main dish that will have your family and friends begging for more.
I have been eating lamb pretty much for as long as I have been eating solid foods. Lamb was one of my mom’s very favorite foods, right alongside angel food cake.
She loved lamb served just about any way, but her favorite was always leg of lamb. This is partly because it is what my great-grandmother always made, and partly because she thought that other cuts – such as lamb chops – were a lot of work for a small amount of meat.
This is my great-grandmother’s roasted boneless leg of lamb recipe that she passed on to Momma and is the same recipe we enjoyed my entire childhood. Momma would always make it for Easter and occasionally at other times throughout the year.
It’s easy, incredibly delicious, and downright impressive. Make sure this is on your next holiday or dinner party menu! It’s sure to be the star of the show.
My Great-Grandmother’s Boneless Leg of Lamb Recipe
The recipe for this boneless leg of lamb is jotted down in my great-grandmother’s handwriting on an old piece of stationary. It’s discolored from age and from being folded and unfolded about 100 times.
It has always had a treasured place in my mom’s recipe box, which is now my own.
The story goes that, after moving out on her own, my mother called Ma-Ma (her grandmother) to get the recipe. Ma-Ma talked her through it on the phone, then mailed her this piece of paper the next day.
It includes a vague ingredient list, the words “Proceed as previously instructed” and “good luck” at the bottom. The “good luck” has always made me giggle.
I spent enough years watching Momma make this recipe that it’s been ingrained into my memory.
The flavors are simple and classic: garlic, herbs, and lots of lemon. The procedure is as simple as can be. But the final result?
So downright delicious.
If this is your first time making lamb, especially leg of lamb, don’t be intimidated. We’re going to talk through it so you can knock the socks off of anyone who tries this!
How to Roast a Boneless Leg of Lamb
Whether you’re making this for Easter, a fancy dinner party, or as a special birthday meal, this roasted boneless leg of lamb is an easy recipe that is sure to be a hit.
Ingredients you’ll need
To make the lamb, you will need:
- Boneless leg of lamb roast: My mom’s go-to was always a boneless leg of lamb due to ease and price. Most boneless legs of lamb will be in the 3-5 pound range. Plan for about ½ pound of meat per person. You can also make this recipe with a bone-in roast.
- Garlic cloves: We’ll need 5 garlic cloves. Some of these will get inserted into the roast itself, while others will get minced up for the rub.
- Rosemary: You can use dried or fresh rosemary. If using fresh, make sure to mince it finely. No one wants a giant piece of chewy rosemary in their lamb.
- Thyme: Again, you can use dried or fresh thyme for this rub.
- Fine sea salt: We will use plenty of salt to help flavor the lamb. My preference is fine sea salt, although kosher salt will work great, too.
- Black pepper: Lots of black pepper is always a must in our house! Make sure to use the freshly-ground stuff for the best flavor, please.
- Lemon juice: We’ll need freshly squeezed lemon juice from 2-3 lemons for the rub. If your lemons are large and/or very juicy, use 2. If they are on the smaller side or not very juicy, use 3.
If you are using a bone-in roast, they will typically be in the 5-7 pound range, with the bone being about 2 pounds of that.
This next bit is something I have added to this recipe, but I think my great-grandmother and mother would approve: Potatoes!
If you’d like, you can roast some potatoes in the fat that renders off of the lamb during cooking. To do this, you will need:
- Fingerling potatoes or small roasting potatoes: I use about 1 ½ to 2 pounds of potatoes for about 4 people.
- Olive oil: Even though the potatoes will cook in the lamb drippings, a little olive oil helps get the roasting process going.
- Big pinch of fine sea salt: Again, fine sea salt is my preference here, but kosher salt is great, too.
Keep in mind that the potatoes are totally optional. Feel free to skip them if you prefer doing roasted garlic mashed potatoes instead.
Making this recipe
If you are using a boneless leg of lamb, you will need to prep your roast.
Most boneless leg of lamb roasts come netted. We need to remove this netting because if we leave it on, it will pull off the beautiful crust after roasting.
Cut off the netting, then use a few pieces of cotton kitchen twine to hold the roast together. This does not have to be done in a fancy way – you just want to keep the roast held together.
Note that if you are using a bone-in roast, you can skip this step.
Check the fatty side of the roast. If there are any really thick spots of fat, feel free to trim those, but do not remove all of the fat from the lamb.
Place the roast in an oiled roasting pan, fat-side up.
Slice 3 of the garlic cloves into thick slices. I like to do about 4 slices per clove. Use a sharp knife to cut slits into the roast and place a slice of garlic into each one.
Roughly chop the rest of the garlic and add it to a mortar along with the herbs, salt, and pepper. Use the pestle to work this into a paste, then add the lemon juice and use the pestle to combine.
If you don’t have a mortar and pestle, finely grate or mince the garlic and stir it together with the herbs, salt, pepper, and lemon juice.
Pour this mixture all over the lamb roast, rubbing it in with your hands. Make sure to get it onto every part of the roast!
Let the lamb rest for 30 minutes while you preheat the oven to 325℉.
If you are adding the potatoes, do that now. Cut the potatoes into equal pieces (I halve or quarter them, depending on their size) and toss them with the olive oil and a big pinch of salt.
Place the potatoes in the roasting pan around the lamb.
Cook the boneless leg of lamb until the internal temperature is 5-10℉ shy of your target cooking temperature. We like our lamb medium rare, so we aim for 5-10 degrees shy of 130-135℉.
This will take about 20 minutes per pound of meat.
Remove the roast from the oven. Loosely tent it with foil and let it rest for 15-20 minutes before slicing and serving the lamb. The internal temperature of the lamb will continue to increase those final 5-10 degrees while it rests.
If you want your potatoes to be more browned/caramelized, simply remove the lamb roast to a platter to rest and return the pan with the potatoes to the oven until you’re ready to serve.
Internal Temperatures and Cooking Times for Leg of Lamb
We have always liked our boneless leg of lamb to be served medium rare. And most chefs will agree that medium rare to medium is just perfect.
But when you make your lamb at home, you get to choose how you like it to be cooked!
Below are internal temperatures and approximate cooking times for boneless leg of lamb roasts:
- For rare: 125℉, about 15 minutes per pound
- For medium-rare: 130-135℉, about 20 minutes per pound
- For medium: 135-140℉, about 25 minutes per pound
- For well-done: 155-160℉, about 30 minutes per pound
Please keep in mind that the USDA recommends cooking all cuts of lamb (except for ground lamb) to 145℉, which is on the higher end of medium.
If you are using a bone-in roast, the bone can make the meat cook slightly faster, so plan on about 5 minutes less cooking time per pound for a bone-in leg of lamb.
When you are taking the internal temperature of the meat, insert an instant-read or meat thermometer into the center of the thickest part of the roast. If cooking a bone-in roast, make sure the thermometer does not touch the bone.
The ends of the roast will always end up a bit more done than the center. This is perfect when serving a crowd; those who prefer their meat more done can take a slice from the ends, and those who prefer theirs more rare can take one from the middle.
Serving Suggestions
There are lots of ways you can serve your roasted leg of lamb. I have seen many people use the drippings from the roast to make a gravy, although that is not my personal favorite way to enjoy it.
Lamb, especially leg of lamb, is a richer cut of meat, so I like to serve it with something that will help brighten the dish. It’s no surprise that it’s super common to serve lamb with mint!
When I was growing up, we ate our leg of lamb with mint jelly. It was the store-bought kind and was bright green and honestly, I can still get down with that.
But these days, we really enjoy serving our lamb with a simple mint chimichurri. It is bright and tangy and is the perfect complement to the richness of the lamb.
Recipe FAQs
Roasted Boneless Leg of Lamb
Ingredients
For the lamb:
- Boneless leg of lamb roast about 3-5 pounds (see notes)
- 5 cloves garlic peeled, divided use
- 1 teaspoon dried rosemary or 1 tablespoon fresh rosemary, chopped
- 1 teaspoon dried thyme or 1 tablespoon fresh thyme
- 1 tablespoon fine sea salt
- 1 teaspoon freshly ground black pepper
- 2-3 lemons juiced (see notes)
Optional for roasting:
- 1.5-2 pounds fingerling or small roasting potatoes
- 1 tablespoon olive oil
- Big pinch of fine sea salt
Instructions
- Remove roast from the refrigerator. Most boneless legs of lamb roasts will come netted. Remove the netting, then use 2-3 pieces of kitchen twine to hold the roast together. If you are using a bone-in roast, you will not need to tie it.
- If there are any thick spots of fat on the roast, feel free to trim these if desired, but do not remove all of the fat from the roast.
- Place the roast in an oiled roasting pan.
- Cut 3 of the garlic cloves into thick slices, about 4 per clove. Use a sharp knife to cut slits into the roast; place 1 slice of garlic into each slit.
- Roughly chop the remaining 2 garlic cloves. If you have a mortar and pestle, add to the mortar along with the rosemary, thyme, salt, and pepper. Use the pestle to work this mixture into a paste. Add the lemon juice and use the pestle to work the paste into the lemon juice.
- If you do not have a mortar and pestle, very finely mince or grate the garlic cloves and add to a bowl with the rosemary, thyme, salt, pepper, and lemon juice. Stir to combine.
- Pour this mixture over the lamb roast, rubbing it all over the roast with your hands.
- Let the roast rest for 30 minutes while you preheat the oven to 325℉.
- If desired, while the lamb rests, wash the potatoes and halve or quarter them, depending on their size, to cut them into roughly equal-sized pieces. Toss with a tablespoon of olive oil and a heavy pinch of fine sea salt and add to the roasting pan around the lamb.
- After 30 minutes, place the roasting pan in the oven. Cook at 325℉ until the internal temperature of the roast reads 5-10 degrees shy of 130-135℉ for medium rare, about 20 minutes per pound. (See notes for other temperatures.)
- Remove the pan from the oven. Loosely tent with foil and rest for 15-20 minutes before slicing and serving. As the lamb rests, the temperature will continue to increase the final 5-10 degrees to medium rare.
- If you add the potatoes and wish for them to be more caramelized, remove the lamb to a cutting board or platter to rest, then turn all of the potatoes cut-side down in the pan. Return the pan with the potatoes to the oven while the lamb rests.
- Serve lamb with mint chimichurri.
Notes
- For rare: 125℉, about 15 minutes per pound
- For medium-rare: 130-135℉, about 20 minutes per pound
- For medium: 135-140℉, about 25 minutes per pound
- For well-done: 155-160℉, about 30 minutes per pound