This delicious Slow Roast Leg of Lamb recipe is boneless, marinated overnight and slowly roasted to perfection. You’ll be rewarded with the most tender, succulent lamb that is totally worth the wait!
Slow Roast Leg of Lamb
If you’ve never been a fan of lamb before, this recipe is sure to make you love it. This is the best way to cook lamb! The vinegar based marinade tones down the gaminess of the lamb and, paired with the slow roast, creates the most incredibly flavored and tender meat.
Growing up, my mom only used to make lamb for Easter or sometimes for Christmas, but that’s about it. She never liked lamb, still doesn’t, but she’d always cook it for my dad. I decided then that I didn’t like lamb. But then I got married, and hubs is a big fan of lamb which is why I started cooking it more often.
This recipe made a believer out of me! I am now a huge fan of lamb. Lamb can be quite costly, which is why if you’re going to spend the money, you might as well do it right. You’ll have one unforgettable dinner, plus you’ll be a rockstar!
Ingredients
Keep scrolling to the recipe card for a list of FULL ingredient amounts and instructions or click the “Jump to Recipe” button at the top of the page!
- Onions
- Fresh rosemary
- Fresh parsley
- Garlic
- Salt & pepper
- Olive oil
- White vinegar
I used white onion for this recipe, but any type will work. If you wanted to change the flavor a bit, using red or white wine vinegar would be amazing as well. For marinades, I prefer to use fresh herbs. You don’t need any heat to really pull out all that awesome flavor!
For the lamb you will need:
- Leg of lamb, boneless or bone-in
- Garlic
- Chicken broth
- Olive oil
- Water
For the gravy you will need:
- Tomato paste
- Cornstarch
- Water
How to Make Slow Roasted Leg of Lamb
- Marinate the lamb: Combine all the marinade ingredients in a large ziploc bag. Poke holes in the lamb with a small, sharp knife and insert sliced pieces of fresh garlic into the holes (optional). Add the lamb to the bag, zip it closed, and toss the bag to distribute the marinade evenly. Let it marinate in the fridge for at least 12 hours, and up to 2 days.
- Roast the lamb: Preheat your oven to 350 F. Quarter the onions, smash the garlic cloves, and add them to your roasting pan. Place the lamb on top of the onions, with the fat side up. Discard any excess marinade. Add the chicken broth and water to the pan, then drizzle the olive oil over the lamb. Cover well with foil and bake for 4 hours. Remove the foil, ladle some juices over the lamb, and return it to the oven for a final hour uncovered.
- Make the gravy: Pour the pan drippings through a sieve into a saucepan. Skim any excess fat. Bring the drippings to a simmer and whisk in the tomato paste. Create a slurry by mixing the corn starch and water together. Pour the slurry into the gravy as it simmers while whisking. You can add more or less of the slurry to create your desired consistency.
How to Make Leg of Lamb in a Pressure Cooker or Slow Cooker
After your lamb has marinated, sear it on all sides. Add the onion and garlic, then place the lamb on top. Add the water, chicken broth, and oil to the pot. Let everything cook on high pressure for 90 minutes, or in the slow cooker on LOW for 10 hours. Put the lamb under the broiler of your oven if you’d like the exterior to be more crisp after it’s done cooking.
Leftovers
Got leftovers? No problem! Store leftover cooked lam in airtight containers in the fridge for 3 to 4 days!
What to Serve With Leg of Lamb
- Italian Parmesan Roasted Potatoes
- Mashed Potatoes
- Old Fashioned Green Beans
- Garlic Parmesan Roasted Brussels Sprouts
- Balsamic Parmesan Roasted Asparagus and Tomatoes
Craving More Lamb? Try These Recipes:
- Herb Crusted Rack of Lamb
- Greek Lamb Burgers
- Rosemary and Garlic Leg of Lamb
- Turkish Gozleme with Lamb
- Rosemary Lamb Chops with Garlic Mint Sauce
- Lamb Souvlaki
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Slow Roast Leg of Lamb
Ingredients
Marinade
- 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
Lamb
- 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
Gravy
- 1 tbsp tomato paste
- 1 tbsp cornstarch
- 1 tbsp water
Instructions
Lamb
- 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.
Gravy
- 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.
Video
Recipe Notes
- Although I used a boneless leg of lamb, you could use one with bone in. Lamb shoulder would also work in this recipe.
- Roasting time may differ based on the weight of the lamb.
- Store leftover lamb in an airtight container in the fridge for 3 to 4 days.
My family has raised lamb for over 100yrs. So, as you might imagine, we were introduced to it at a very young age. Today, after picking my mint to make mint jelly, I pulled out a small leg roast and am going to use your recipe. The house is very much smelling like a good meal in the works! I’ll be using garden grown onions, red and yellow carrots, purple potatoes, and asparagus to accompany this. My mouth is watering in anticipation. How will I ever make to tomorrow night!
Fabulous recipe Jo, I have made this specifically for making “Gyros”…yum, soooo good!!! I really love all your recipes and look forward to seeing more …..I am a happy camper when you show up in my mail box….Love you….Hugs , Loretta
That’s fabulous, we’re so glad you love the recipe!
I’ve used a similar marinade for years for lamb. In place of the vinegar I use lemon juice and grill the lamb on a grey coal fire for aprox 30 min. Meat is unbelieveably tender and flavorful. I used a mince sauce since it’s difficult to make a gravy from grilling.
I’ll have to try this next time, Helen. 🙂
Five hours seems like a long time. What should the internal temperature be when done? Looking forward to trying this in next few days. Thanks for the recipe!
We’re not looking for a medium rare roast- we’re looking for fall-apart tender lamb. You can reduce the temperature if you’d like, but 5 hours is really what we’re looking at to achieve that tender meat.
Wowza this was good. I have to say that lamb is usually not my go to meat, a little too gamy for me but this marinade made the difference. I marinaded for 24 hrs with a 3lb boneless leg of lamb and there was no gamy taste at all.
I did use an in oven meat thermometer and it reached 165 degrees within 2 hours.
What was even better was the sauuuuuuce. I will admit that when I saw tomato paste I was thinking it was going to taste like tomato sauce but it’s far from it. Both hubs and I really enjoyed this a lot. Thanks Jo for another great recipe!
Oh I love hearing this, it seriously makes me so happy. I know I was a bit skeptical on the tomato paste but I wanted to try it and it really did work. 🙂 The vinegar in the marinade is what gets rid of that gamy taste, so so happy you guys enjoyed this!
I made this for lunch today – marinated overnight, and in the oven by 8 am. Leg of lamb was on offer for £7/kg, so a bargain price. Since I didn’t want to invest a huge amount just in case hubs didn’t like it, I got a small part leg (just over 1 kg weight). I took the bone out, but left in the roasting tin for flavor.
It was a definite hit. Gravy was nice, and I served with a baked potato (in the oven during the browning time) and peas. Just enough left over for a healthy sandwich – and we ate well. Will post some pictures on Instagram in a bit.
Best lamb I’ve ever cooked – will definitely be making this again, with a larger leg next time!
Hi Connie! So happy you enjoyed this recipe, and I’m looking forward to seeing the pictures on Instagram. 🙂
We grew up eating lamb on my grandparent’s ranch. Delicious recipe!
Who knew such a gorgeous dish was this easy to make. My husband will be so happy when i make this.
Perfect dinner any night of the week!
We are making this a regular meal at our house now!
Wonderfully tender, and so perfect for holidays!
Looks wonderful , thanks for sharing
So tender and flavorful!
Question? Do you think you could cut the lamb leg into two or three portions? Prepare one portion and freeze the other portion? Adjusting the marinade and roasting time acordingly?
A 5 lb piece of lamb is a little too much for two servings, but I would like to try this recipe. I think marinating the lamb is a great idea.
What do you think? Thanks for your help.
You can definitely do that. With a piece that small I’d roast it for about 1 hour.