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overhead shot of slow roasted leg of lamb on a plate with mashed potatoes brussel sprouts and asparagus
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4.69 from 29 votes

Slow Roast Leg of Lamb

This delicious Slow Roast Leg of Lamb is marinated overnight and slowly roasted to perfection. You'll be rewarded with the most tender, succulent lamb that is totally worth the wait!
Prep Time15 mins
Cook Time5 hrs
Marinate time12 hrs
Total Time5 hrs 15 mins
Course: Main Course
Cuisine: American
Keyword: holiday recipe, lamb, leg of lamb, slow roast leg of lamb
Servings: 8
Calories: 451kcal



  • 2 medium onions white, diced
  • 2 tbsp rosemary fresh, chopped
  • ¼ cup parsley fresh, chopped
  • 3 cloves garlic minced
  • 1 tsp salt or to taste
  • ½ tsp pepper or to taste
  • ½ cup olive oil
  • ½ cup white vinegar


  • 5 lb leg of lamb boneless
  • 4 cloves garlic cut in long strips
  • 2 medium onions quartered
  • 3 cloves garlic smashed
  • 1 cup chicken broth low sodium or no sodium added
  • ¼ cup olive oil
  • 1 cup water




  • Prepare the marinade by combining all of the marinade ingredients in a large ziploc bag.
  • Poke holes in the leg of lamb and insert a piece of the garlic that's cut into long strips, in each hole. This step is optional, but it gives the lamb a more garlicky flavor.
  • Place the leg of lamb in the ziploc bag, close it and toss it around so that the marinade goes all around the leg. Place the ziploc bag in the fridge and let it marinade overnight. I would recommend at least 12 hours to 2 or 3 days.
  • The next day, preheat your oven to 350 F degrees.
  • Place the quartered onions and smashed garlic in a large metal roasting pan then place the leg of lamb on top of the onions, fat side up. Discard the rest of the marinade. Add the chicken broth to the pan, the olive oil, drizzling some over the lamb, and the water. 
  • Cover the pan with aluminum foil and place the roasting pan in the oven. Roast the leg of lamb covered for 4 hours. Remove the aluminum foil from the pan and using a ladle, spoon some of the pan juices over the lamb. Place the pan (uncovered) back in the oven and roast for an additional hour or until well browned.
  • Remove the lamb from the pan onto a platter. 


  • Skim some of the fat from the pan drippings using a large spoon. 
  • Place the pan on the stove over medium-high heat. Add the tomato paste when the liquid starts to bubble. In a little bowl whisk together the cornstarch with the water, then add it to the pan. Whisk everything together. There should be at least a couple cups of liquid in the pan, but if most of your liquid has evaporated, add more chicken broth or water. I only added 1 tbsp of cornstarch because I wanted a thinner gravy, but feel free to add more until you reach the desired consistency. Cook for a few minutes, until the gravy thickens a bit.
  • Strain all the liquid into a bowl, then press all the liquid out of the onion and garlic using a spatula, for additional flavor.
  • To serve, use two forks or tongs to tear or shred the meat and serve with the gravy over mashed potatoes or with roasted vegetables.



  1. Although I used a boneless leg of lamb, you could use one with bone in. Lamb shoulder would also work in this recipe.
  2. Roasting time may differ based on the weight of the lamb. 
  3. Store leftover lamb in an airtight container in the fridge for 3 to 4 days.


Calories: 451kcal | Carbohydrates: 8g | Protein: 38g | Fat: 28g | Saturated Fat: 5g | Cholesterol: 114mg | Sodium: 432mg | Potassium: 675mg | Fiber: 1g | Sugar: 2g | Vitamin A: 215IU | Vitamin C: 8.7mg | Calcium: 43mg | Iron: 4mg