Boneless Leg of Lamb

You might not be aware yet. To roast boneless leg of lamb is my favourite way to celebrate anything. I love cooking deboned lamb because it’s so EASY but looks GRANDE on the table. Yes, it is super simple and hard to mess up.

I created this the best ever basic boneless roasted leg of lamb recipe about 15 years ago. And I make it for a special occasion. Or when I need to leave a lasting impression. Works every time.

Last time was my visiting mom that “doesn’t like” lamb. And a time before I made this roast to say “thank you” to the nicest plumber on Earth. Everyone loves it! And I will teach you how to cook the most perfect boneless leg of lamb in the oven. For Holidays, Easter dinner or a weekend dinner. You can do it!!!

Buying Best Lamb

Lamb is expensive. Like any red meat. Like any meat. So understand your fear of “screwing it up”. You will not. Boneless lamb is actually the easiest meat to roast. I still don’t know how to make a beef roast. Not to mention how to cook a prime rib.

When it comes to buying lamb I turn to Costco. I am not fancy enough or do not have time to go to a butcher shop. Frankly, I think those days are behind us. Plus I do not see a difference in meat unless it’s organic or locally raised etc.

Kirkland boneless leg of lamb from Costco does it for us. The cost is about $8 per pound. And 99% of lamb sold in Canada I ever saw is from Australia.

Bone In Vs. Boneless Leg of Lamb

I prefer and highly recommend to use boneless leg of lamb for many reasons:

It is easy to fit into a roasting pan.
It is easy to carve.
You get more meat.
And it probably cooks faster.

How Long to Cook Boneless Leg of Lamb?

How long do you cook a boneless leg of lamb? Cooking time depends on how you like your meat. Just like with steak.

It all comes down to checking often after a certain period of time. My best advice is:

For 4-5 lbs roast check internal temperature with a meat thermometer after 1 hour and go from there.
For 2-3 lbs roast, check after 45 minutes.

Below are listed cooking times per pound.

Medium Rare: 120 F to 130 F internal temperature – about 14 minutes per pound
Medium: 130 F to 140 F internal temperature – about 16 minutes per pound
Well-Done: 140 F to 150 F internal temperature – about 18 minutes per pound

Remember meat will keep “cooking” as it rests.

More Tips for Cooking Time:

The key is to check often with an internal meat thermometer.
Please keep in mind internal temperature will rise while meat is resting after baking in the oven.
All ovens vary: age, electric vs. gas. Not to mention convection oven cooks food faster.
Bake uncovered.

What Temperature?

I know there is a slow roasted lamb cooking method at low 300 degrees F temperatures. My boneless lamb roast is baked at 425 degrees F. I think it yields juicy meat inside with browned outside within a reasonable amount of time.

Below is lamb cooked for 18 minutes/lb which ended up being well done after resting.

Boneless Lamb Roast FAQs and Tips

Do I have to marinate the lamb?

No. Lamb is tender meat. You just need to season it properly. My absolute favourite classic seasonings are garlic and rosemary. Maybe a squeeze of lemon at the end. So, no lamb marinade recipe to follow. Yay for simplicity.

Can I use boneless lamb shoulder?

Yes. I have done it many times. It depends what’s at the store when I’m there. SImple as that. I believe boneless lamb shoulder is even cheaper than the leg.

Can I use fresh rosemary instead of dried?

Yes. I use both fresh and dried rosemary with this recipe. One time I bought a bunch of fresh rosemary for making boneless turkey breast roast. It lasted a month in the fridge. Long enough for “the super nice plumber” dinner. But not long enough for “not liking lamb mom” dinner. So I have tried both many times.

What to do with all that fat?

Lamb is extremely fatty meat. You will see a lot of fat solidify at the bottom of the roasting pan pretty much immediately as it starts to cool off. And if you refrigerate leftovers, fat will solidify nicely into white chunks. I take this as an opportunity to discard extra fat and remove it before serving or reheating.

Plan ahead

Cooking boneless leg of lamb in the oven IS easy! It just needs enough cooking time. In our days of sheet pan dinners, one pot meals and Instant Pot I recommend to plan ahead with this recipe. Just make sure you understand your dinner will be on the table in 2 hours if you roast lamb.

I speak from my own experience. I was “caught off guard” a bit once last month.:) We ended up drinking a lot of wine and beer with a super nice plumber guy. It was a pleasure anyways.

How to Roast a Boneless Leg of Lamb

1. Season with Rosemary and Garlic

In a medium roasting pan or Dutch oven, place deboned leg of lamb roast and make 15 inserts with a paring knife.
Stick garlic slice into each opening until you run out of garlic.
Rub roast with oil all around.
Then sprinkle one side with half of rosemary, salt and pepper.
Turn around and repeat on another side.

2. Bake Uncovered

Bake uncovered according until desired doneness.

Medium Rare: 130 F to 135 F (about 12 minutes per pound)
Medium: 135 F to 140 F (about 15 minutes per pound)
Well-Done: 155 F to 165 F (about 20 minutes per pound)

My best advice is for 4-5 lbs roast to check internal temperature after 1 hour and go from there. For 2-3 lbs roast, check after 45 minutes. It all comes down to checking often after a certain period of time.

3. Let Rest and Carve

Remove lamb roast from the oven and let rest uncovered for 15 minutes. Do not skip!
Transfer on a cutting board.
Using a sharp knife, remove the casing and slice into 1/4 inch slices against the grain. Thin slices of lamb taste better than thick ones. My husband is guilty here.

What to Serve with Leg of Lamb?

Healthy mashed potatoes – so classic and satisfying.
Cauliflower mashed potatoes – low carb alternative.
Cucumber and tomato salad – cucumber and lamb are a match made in heaven.
Grilled vegetables – if it’s grilling season wherever you are.
Healthy spinach salad – can never go wrong with this simple salad.