Gabriel Woods
Published by Gabriel Woods
Last Updated On: April 13, 2023

As an experienced chef and avid meat enthusiast, I’ve grown very fond of lamb roast's rich flavors and textures.

With over 10 years of professional culinary experience and a deep passion for exploring the art of cooking, I have perfected a roast lamb recipe that will impress even the most discerning palates.

Slow Roasted Boneless Leg of Lamb Recipe with Garlic and Thyme

A close up image of slow roasted boneless leg of lamb

If you enjoy eating lamb, then this slow roast is an amazing recipe that makes a great meal - whether as a celebratory roast or a simple family dinner.

1. Recipe Overview

  • Prep Time: 30 minutes
  • Cook Time: 2 hours 30 minutes
  • Total Time: 3 hours
  • Number of Servings: 6-8

2. Ingredients:

  • 1 boneless leg of lamb, about 4-5 pounds
  • 6 garlic cloves, thinly sliced
  • 2 tbsp fresh thyme leaves
  • 2 tbsp olive oil
  • 2 tsp kosher salt
  • 1 tsp black pepper
  • 1 lb baby potatoes, halved
  • 4 sprigs of chopped rosemary
  • 1/2 lemon, zested

3. Instructions:

  1. Preheat oven temperature to 325°F (160°C).
  2. Remove the leg of lamb from the refrigerator and let it sit at room temp for about an hour.
  3. In a small bowl, combine garlic slices, thyme leaves, olive oil, salt, and black pepper to make a wet rub.
  4. Pat the lamb dry with a paper towel and season the meat generously with the rub. Rub the mixture all over the meat, making sure to cover it evenly.
  5. Place lamb leg in a roasting pan, fat side up, and add the halved potatoes around it.
  6. Scatter the fresh rosemary sprigs on top of the lamb leg and sprinkle the lemon zest over everything.
  7. Roast the leg of lamb in the oven for about 2 hours and 30 minutes, or until the internal temperature reaches 135°F for medium-rare doneness or 145°F  for medium lamb [1].
  8. Remove the meat from the oven and let the roast rest on a roasting rack for 20-30 minutes. This allows the juices to redistribute and makes the meat more tender.
  9. While the lamb leg is resting, place the pan over medium-high heat and add 1/2 cup of water to deglaze the pan. Scrape up any brown bits and let the liquid simmer until it reduces and thickens into a delicious au jus.
  10. Carve the roasted meat into big slices and serve immediately with the roasted potatoes and pan drippings on a serving platter.

"Forget about cooking complicated dishes: with a good quality cut of lamb, some seasonal herbs and spices, you can create something truly amazing."
- Delia Smith, English Chef

Recipe Notes

A lamb roast recipe in bone-in leg style
  • Add about 30 minutes to the cooking time for a bone-in leg of lamb. The bone in the bone-in lamb leg acts as an insulator and slows down the transfer of heat throughout the meat [2].
  • You can add other vegetables like carrots and onions to the roasting pan for a one-pan meal.
  • If using a butterflied leg of lamb, reduce the time in the oven to about an hour and a half.
  • Dijon mustard, olive oil, and balsamic vinegar may also be used as wet rub ingredients.
  • You can cook both lamb, potatoes, and vegetables in the same pan during the roasting process.
  • Make sure to buy market-weight meat from a reputable butcher for the best quality.
  • Letting the lamb rest after reaching the desired temperature is essential for optimal juiciness and tenderness. You can cover it loosely with aluminum foil as you allow it to sit, so it loses less heat.
  • You can serve leftovers cold as a delicious sandwich filling or combine them with ingredients like mayo and slaw-type greens or diced onions and spices the next day.

Dishes to Serve with a Lamb Roast Main Course

  • Roasted vegetables like carrots, onions, and Brussels sprouts
  • Creamy mashed potatoes
  • Grilled asparagus
  • Green beans with lemon
  • Homemade dinner rolls
  • Red wine or a robust beer

Tips For the Best Lamb Recipes

A top view of raw lamb leg
  • Let the meat come to room temperature before cooking lamb. This aids in even cooking.
  • Always use a meat thermometer to ensure the lamb is cooked to your desired doneness. Oven temperatures can vary, and overcooking can quickly occur, so it is better to err on the side of caution.
  • Garnish with fresh herbs for extra flavor. For added depth of flavor, you can put fresh rosemary sprigs into the interior before roasting lamb.
  • To reduce saturated fat and reduce the mutton flavor, have the butcher trim the thick outer layer of fat from the whole leg before roasting.
  • Getting a lamb cut with the shank attached (also known as American leg or shank-on leg) lets you create bone broth with so much flavor.
  • To increase monounsaturated and polyunsaturated fat, drizzle with olive oil before serving.
  • I recommend covering the slow-roast lamb with foil to keep it moist. However, during the last 30 minutes of roasting, removing the foil from the roasted leg makes the skin crispy. Or, like you would with a beef roast, turn on the broiler element for the last 5-10 minutes of roasting for a crispy skin.
  • Before roasting, you can drizzle the lamb in oil or a butter and oil mixture to help keep the meat moist and add richness to the flavor.


What Seasoning Is Best for Lamb?

Of course, the best seasoning for lamb depends on personal taste. However, lamb goes well with dried rosemary, dried mint, oregano, thyme, and other dried herbs.

Garlic powder, cumin, chili powder, coriander, paprika, and mustard powder also work well.

How Do You Keep Lamb Moist?

You can keep your lamb moist by adding stock to the roasting tray and covering the roast with foil. Roast at a lower temperature for a longer period of time, and let the fat melt and baste the roast.

Mastering Your Lamb Roast

A perfectly cooked lamb roast can be the highlight of any holiday meal or dinner party. With the right recipe and technique, you can create a dish that is juicy, tender, and full of flavor.

Of course, the best way to start a recipe is by using the freshest and highest quality lamb.

If you don’t know where to start, try Crowd Cow - a meat delivery company that provides free-range, humanely raised, GMO-free lamb straight to your door.

The company sources its meat from independent farms across the US and offers flexible shipping options.


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