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!
A Delicious Holiday Dinner
A roast leg of lamb is a festive dish for whatever holiday you’re celebrating. For us, Christmas dinner is always a bit up in the air—sometimes it’s Grandpa’s turkey, sometimes it’s our famous Prime Rib. And sometimes, we make a roast leg of lamb, which is a really special treat!
The flavorful crust includes garlic, rosemary, sage, and whole grain mustard, as well as lots of salt and black pepper. The lamb makes a delicious and flavorful jus, perfect for pouring over the top of the roast meat and any potato side dish.
What to Serve with Lamb: Mint Jelly or Sauce? Gravy or Jus?
The Mint Element:
Mint jelly is usually found on the table with lamb roast because it has a fresh flavor that provides a contrast to the gamey taste of the lamb.
Mint is also used in many Middle Eastern lamb dishes. I personally never cared for mint jelly, so I made an alternative sauce—a mint lemon dressing that works perfectly alongside the meat.
Gravy vs. Au Jus
Au jus is our preference for roast leg of lamb. Au Jus literally means “with juice” in French—the pan juices or natural juices from roasting on a bed of onions with herbs and aromatics. There are a few steps in preparing and seasoning the jus, so pay attention to those steps in the recipe.
For those of you who prefer gravy, you can follow our recipe for our homemade turkey gravy recipe and watch the tips and tricks on our Youtube video on how to make Turkey gravy with drippings.
Use the roasted lamb pan drippings, and follow the same directions, but for roasted lamb gravy, use beef stock instead of chicken stock to get the best results.
Lamb Roasting Tips:
1. Take the roast out of the fridge 2 hours before roasting, or up to 4 hours if you like your roast more on the well-done side.
2. Make sure your oven is on the “Bake” setting and NOT on Convection, or this will throw off your cooking times.
3. Check the roast often, and when the bottom of the pan looks dry, add another cup of water as needed every 20 mins. Don’t let the bottom of the pan or the onions burn!
4. Tent the roast with aluminum foil when the top looks like a good roasted color to prevent burning/scorching.
5. When checking the roast temperature, insert the meat thermometer into the thickest part of the roast until it hits bone near the joint.
What Does Semi-boneless Mean?
You’ll see in this recipe that we call for a semi-boneless leg of lamb. That is how it’s sold in our grocery store, and that’s how we prefer it! A semi-boneless leg of lamb has had the hip and leg bone removed, leaving only the shank bone. This balances flavor (roasting on the bone develops more flavor) and convenience, making slicing easier and coking more even.
If you have a boneless leg of lamb, it should be tied by your butcher to make for more even cooking. You’ll also want to check internal temperatures earlier, because it will cook a bit faster!
Oh, and don’t throw away the leftover lamb bone! You can freeze it and make Kaitllin’s lamb soup recipe another day!
Roast Leg of Lamb: Recipe INSTRUCTIONS
Give the lamb leg a quick rinse. 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 evenly and thoroughly all over the roast.
Cover the roast with plastic wrap, and let the roast marinate overnight 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.
Alternatively, you can place everything into a jar, close the cover and shake vigorously for 15 seconds to combine. I like this method because it’s so easy, and you can shake it again in the jar just before serving.
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.
Use the following guidelines for meat temperature. Follow closely for the best results! For those of you having a roast leg of lamb for the first time, we recommend cooking to medium rare to medium, or between 130-135°F, which gives the meat a nice shade of pink and stays very juicy and tender. The lamb’s internal temperature will rise another 5-10°F as it rests. 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.
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 roast 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 roast out at130°F and rest 15-20 minutes – Total roasting time: Approximately 1 hour 40 minutes. (Ready 1 hour after the initial 40 minutes.)
- Medium – take roast out at 135°F and rest for 15-20.
- Well Done – take roast out at 150°F and rest for 15-20 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. You can strain the jus into a gravy separator to remove the grease and serve.
We prefer skimming off the grease and pouring the contents of the pan, onions and all, into a small bowl with a spoon for the table. The caramelized onions are delicious and complement the lamb nicely!
Looking for more authentic recipes? Subscribe to our email list and be sure to follow us on Pinterest, Facebook, Instagram, and Youtube!
Recipe
Roast Leg of Lamb
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
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.
Tips & Notes:
- 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.
