This succulent, flavorful roasted boneless leg of lamb 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.
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
Plan on about 8 ounces (½ pound) of meat per person. If you have a bone-in leg of lamb, the bone will add about 2 pounds to the total weight. Subtract 2 pounds from the total weight of your bone-in roast to determine how many pounds of meat you will have.If your lemons are large and/or on the juicy side, use 2. If they are smaller and/or not very juicy, use 3.My family prefers our lamb medium-rare. If you prefer your lamb cooked differently, follow these internal temperature and cooking time guidelines:
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
When taking the internal temperature of the lamb, insert the thermometer into the thickest part of the roast. If you are cooking a bone-in leg of lamb, make sure the thermometer is not touching the bone, as this will throw off your temperature reading.When cooking a bone-in roast, the bone can make the roast cook slightly faster. Factor about 5 minutes less cooking time per pound for a bone-in leg.