Roast Leg of Lamb

5 from 2 votes

This roast leg of lamb with a garlic, mustard, herb crust is a festive, delicious, and impressive holiday centerpiece, and it cooks in less than 2 hours!

Prep Time20

Cook Time1 40

Marinating time1

Total Time1 2

Course: Main Course

Servings:

Calories: 242kcal

Author: Bill

Ingredients

For the Roast:

6 to 7 pound semi-boneless leg of lamb
¾ teaspoon per pound kosher or coarse sea salt
½ teaspoon per pound freshly ground black pepper
1 teaspoon per pound minced garlic
¾ teaspoon per pound minced fresh rosemary
1 teaspoon per pound finely chopped fresh sage
1 teaspoon per pound stone ground whole grain mustard
½ teaspoon per pound olive oil
3 medium onions same for any size roast cut into 1-inch pieces
Water for roasting pan

For the Mint Lemon Dressing:

3 tablespoons extra virgin olive oil
½ cup fresh mint finely minced
1 teaspoon fresh lemon zest
2 teaspoon lemon juice
¼ teaspoon salt or to taste
¼ teaspoon fresh ground black pepper
Pinch of sugar

US Customary - Metric

Instructions

Rinse the lamb and pat dry with paper towels. In a small bowl, combine the salt, pepper, garlic, rosemary, sage, mustard and olive oil.
Place a shallow roasting rack into a large thick-bottomed roasting pan, and spread the onions evenly in the pan. Place the leg of lamb on the roasting rack, and rub the marinade all over the roast on both sides.
Cover with plastic wrap, and marinate in the refrigerator for 12 to 24 hours. Remove the roast from the refrigerator 2 hours prior to cooking.
Position a rack in the center of the oven, and preheat to 450°F/230°C. Roast for 20 minutes. Add 1 cup of hot water to the bottom of the pan, rotate the pan 180°, and continue to roast for another 20 minutes for a total of 40 minutes.
While the lamb is roasting in the oven, make the mint lemon dressing by whisking together the olive oil, finely minced fresh mint, lemon zest, lemon juice, salt, pepper, and sugar until well-combined and set aside.
After roasting for 40 minutes at 450°F/230°C, turn the oven temp down to 350°F/175°C and continue roasting for another 45 minutes. Check the temperature of the roast with an instant-read thermometer. and continue roasting until the desired temperature is reached. (See note.) We recommend cooking to an internal temperature of 130-135°F, which is medium rare to medium. It should take about 1 hour more after the initial 40 minutes.
Remove the roast to a warm serving plate, lightly cover with aluminum foil, and let the roast rest in a warm place for 15 minutes.
Meanwhile, prepare the au jus: Add 1 cup water or beef stock to the roasting pan and heat on the stove to a slow simmer to deglaze. Add ½ teaspoon salt, or to taste, to balance the sweetness of the onions. Skim off any grease and pouring the contents of the pan, onions and all, into a small bowl with a spoon for the table. Serve alongside the sliced lamb and mint sauce.

Notes

Roast Lamb Finishing Temps:

Make sure you stick the thermometer into the thickest part of the lamb leg for an accurate temperature reading!

Rare - take out at 125°F and rest 15-20 minutes - Total roasting time: Approximately 1 hour 25 minutes - 1 hour 30 minutes. (Ready after 45 to 50 mins after the initial 40 minutes.)
Medium rare - take out at 130°F and rest 15-20 minutes - Total roasting time: Approximately 1 hour 40 minutes. (Ready 1 hour after the initial 40 minutes.)
Medium - take out at 135°F and rest for 15-20.
Well Done - take out at 150°F and rest for 15-20 minutes.

Nutrition