Grilled Butterflied Leg of Lamb

Where to start? Somehow I suspect that the following method – fat is good, flame is good – is going to get me in trouble with some of you. But since this was the best lamb roast I’ve ever eaten in my life, I will forge ahead and tell you how we did it.

The lamb roast was succulent – crusty, flavorful char on the outside, pink and tender on the inside. Many recipes call for trimming off the excess fat from the lamb roast. I did that once to a prime rib roast and have never forgiven myself. Later I learned from my dear mother that “excess fat” was anything more than an inch thick in her book. The fat is needed to make the lamb tender and tasty. Trim it if you must, but leave some on.

Note that the more fat on the lamb roast, the more likely you’ll have flare-ups when you grill. Flare-ups are okay as long as they are controlled and don’t get out of hand. The charring of the outside of the lamb, especially the fatty side, produces amazing flavor. By the way, it used to be that people were worried about char grilling being carcinogenic. Turns out if you marinate the meat in an acid-based marinade first, you negate the cancer-causing elements. (Grillers everywhere rejoice.)

Some people take offense at the very idea of using mint jelly with lamb. I wouldn’t have lamb without it. Homemade mint jelly is fantastic with lamb. And if we’re out, I’ve been known to chop up some fresh mint leaves just to go with the lamb. So, to each her own when it comes to the jelly. What is your favorite way to prepare leg of lamb?

Grilled Butterflied Leg of Lamb Recipe

  • Prep time: 1 hour, 10 minutes
  • Cook time: 1 hour

In this recipe we sear the lamb first, on both sides, grilling on high heat for a short amount of time. Then we cook the lamb on lower heat until it is cooked through. In our opinion, the only way to eat lamb is medium rare or rare. There is nothing more depressing than dried-out, over-cooked lamb. For this reason it is essential that you use a meat thermometer to test the internal temperature of the roast.

Ingredients

  • 1/2 onion
  • 4 cloves garlic, peeled
  • 2 Tbsp fresh rosemary leaves, or 1 Tbsp dried
  • Zest of 1 lemon
  • 1 Tbsp apple cider vinegar
  • 2 Tbsp olive oil
  • Kosher salt and freshly ground black pepper
  • 1 boneless leg of lamb, 5 to 6 pounds, butterflied

Method

1 Put onion, garlic, rosemary, lemon zest, apple cider vinegar, and olive oil into a food processor and pulse to combine. (If you don't have a food processor, just chop the onions, garlic, and rosemary very well and combine with the rest.)

2 Sprinkle a generous amount of salt and pepper over the lamb. Place marinade and lamb into a 1-gallon freezer bag. Spread marinade over all sides of the meat. Seal the bag and refrigerate for 1 to 2 hours.

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3 Remove lamb from refrigerator and let come to room temperature (about 20 minutes). When ready to put on grill, remove from marinade bag. To help make the lamb easier to turn on the grill you can insert a couple of skewers through the lamb, crosswise. (A tip learned from Rick Rodgers in Kingsford Complete Grilling Cookbook.)

4 Prepare grill. If you are using a charcoal grill, prepare the coals so that they are double layered on one side of the grill, and sparsely single layered on the other side of the grill (this is called "banked" grilling). If you are using a gas grill, heat the grill on high on all burners to start. After the initial browning you will reduce the heat.

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5 Place the lamb, fat side down, on the grill on the hot side (double layer charcoals). You will get likely get flareups, so be prepared with a squirt bottle of water or a couple of cups of water (if using a charcoal grill) to control the flames if needed. (My brother Matt swears by shaking the bottle of beer he is drinking to squirt some beer on the coals when needed for flareups.) Sear one side for 4 minutes, then flip the lamb over to sear the other side for another 4 minutes. Then, if you are using a charcoal grill, move the roast to the less hot side of the grill. If you are using a gas grill, lower the heat to low. You will want to maintain a temperature of 300-350°F. Cover the grill and let cook for an additional 35-45 minutes (depending on how thick, and how many pounds the roast is), until a meat thermometer inserted into the thickest part of the roast registers 130°F (for medium rare).

6 Transfer to a cutting board with a well to catch the juices. Cover with aluminum foil and let rest for 5-10 minutes. Remove the skewers if you are using any. Cut across the grain, 1/4 to 1/2-inch thick slices. Serve slices on a warm platter; pour meat juices over the slices. Serve with mint jelly or horseradish. Serves 8-10.

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Lamb roast for this recipe generously provided by the American Lamb Board

Links:
Lamb. The better red meat. - Thoughtful essay from Jo of Amuse Bouche, also a recipe for Lamb Korma with almonds, pecans and sour cream.
The Niman Ranch Cookbook: From Farm to Table With America's Finest Meat
Kingsford Complete Grilling Cookbook
Wikipedia on Grilling

26 Comments

  1. pablopabla

    I don’t know how to roast lamb but I love eating them! The picture of your roast lamb looks sinfully delicious!

  2. Mike

    Wow, this looks great!!!

    I usually just pan-sear lamb in a pan hot and fast then finish it with a blast in the oven. Same concept really.

    I actually am one of the mint-despisers, usually just enjoying the flavor of the meat. I do prepare it with herbs which are usually rosemary or thyme with garlic though.

  3. Gary in Massena

    Elise,

    It does seem that you are getting good use out of your new grill!

    The crunchy goodness on the outside is referred to in BBQ circles as ‘Bark’. Getting between a BBQer and Bark results in a similar issue of getting between Momma bear and her cubs.

    Fat (in BBQ) is GOOD. It makes things self-baste which results in the juicy result. And, since it renders out in the cooking process you don’t have to feel quilty about it. You probably noticed that the resulting roast was not too fatty.

    Flare ups from the fat hitting the coals can be a problem though if it stirs up ash which can then contaminate the product. After your initial sear you can always try putting the roast over a drip pan to solve this issue.

    Great job. I now can’t wait until lunch (teaches me to check my food blogs out this early in the morning).

    Gary in Massena.

  4. Jerry

    Unfortunately, I haven’t had the opportunity to cook a leg of lamb as of yet. I’ll definitely keep this recipe handy, however. It looks amazing!

  5. Madam Chow

    Yes! I, too, have learned the hard way to leave the fat on! I just did that recently with a roast leg of lamb – I didn’t trim a thing, and my husband said it was one of the best grilled legs of lamb he’s ever had.

  6. Kelly Mahoney

    Without the fat, it will come out tasting like a shoe. My mom taught me that one.

    This looks so good.

  7. Mary

    I’ve made leg of lamb on the grill like this for year, but I have always taken as much fat off as I could. I’m going to try it this way next time. I don’t mind the mint jelly eaters and sometimes use the rosemary garlic combination, but sometimes I make it Moroccan style with a cumin/coriander seed rub and harissa and yogurt with cucumbers on the side (though I do put mint in with the yogurt).

  8. Alanna

    If Elise is positively effusive with words, it’s got to be good!!

  9. karen

    Hi, I don’t have a grill. Can I cook this in the oven instead?

  10. Joy Case

    The only way I’ll eat it is to make a paste of a coarse ground mustard like Grey Poupon, mixed with fresh thyme,rosemary, oregano, garlic, salt and pepper etc or what ever herbs and spices you prefer. I cover the inside of the butterflied roast with this mixture. Roll it up and tie it. If I have any of the mustard mixture left, I brush some on the outside before I sear on a grill over high heat and then finish over med heat until med-rare. Oh and I never trim the fat.

  11. Stephanie

    Fat=Flavour.
    And that lamb looks amazing! Love the skewer trick too.

  12. Rita

    Sometimes Fat Rocks!! This is definitely the case with lamb and prime rib.

    Elise you’re making my mouth water!

  13. phyllis

    Some roasted fennel, or eggplant and a white bean salad with some olive oil and shallots or red onion, would be in keeping with this grilled lamb. Or, in the winter, some potatoes, scalloped, of course.

  14. Brett

    The photo of your roast lamb looks so delicious I can practically taste it. And yes, I agree, keep the fat on!

  15. Lisa

    You won’t get into any trouble with me! Love the “fat” comment from your mom. How true! This looks simply amazing. I adore lamb. Maybe I’ll work up the nerve to try grilling a leg o’ lamb.

  16. Steamy Kitchen

    lamb….fat….grill….

    I think I’m in love!

  17. carmen mooney

    We had the grilled lamb last night with the fingerling potatoes you posted recently. I marinated the leg of lamb overnight and added red wine from an opened bottle until the leg was completely covered with the wine and marinade sealed in a gallon size bag. The potatoes along with fresh sliced tomatoes and home made biscuits.

    These two recipes may become weekly meals. So easy, so delicious.

    How very grateful we are to you for sharing so many wonderful recipes. Almost daily I use one of your recipes. I printed so many of yours and some others that I need to organize them in a binder or something. Any ideas?

  18. mike

    To the person who asked if it may be cooked in an oven because they don’t have a grill. I myself live in an apartment building and unfortunately do not have yard space for a grill. But I absolutely love a leg of lamb so the answer is yes. I dice up a garlic clove. I cut slices in the roast and shove the bits of garlic in the slices before cooking. Scatter your slice depth, some quarter way through and some deeper and some more shallow. You do not want the garlic all concentrated in one section of the roast. I do it all the way around. Heat oven to 350 degrees. Cook fat side up for about 40 minutes. Size of roast varies cooking time so check after about 30 mins. I absolutely agree though that lamb can not be cooked more then medium rare.

  19. Dawn

    We will be trying your recipe on Mother’s Day we will be having family over to share this wonderful leg of lamb. I can’t wait to try it!!

  20. Jess

    This looks delicious,
    So far my favourite lamb as been a slow cooked one with classic rosemary, garlic and ginger but smothered in mint jelly and cooked on high for a while at the end of cooking. I think I’m going to do it this way next time though.

  21. Dan

    Very good. Next time I will add a little bit more vinegar and salt. Thanks for sharing.

  22. Pam

    Just made our favorite grilled butterflied leg of lamb yesterday. Recipe: 4-5 pound boneless leg of lamb; marinade: 3/4 cup soy sauce, 1 cup red wine, 1 tablespoon cracked black pepper, 2 tablespoons chopped fresh rosemary, 1/2 cup chopped fresh mint, 4 large cloves garlic, minced. Mix marinade ingredients and pour over opened and flattend leg of lamb in 9×13 inch glass pan or very large zip lock bag, marinate 2-6 hours, turning over several times.
    Grill over indirect medium high heat. I place lamb over center burner of three burner gas grill, middle burner off. Grill 20-25 minutes each side for medium rare. Let meat rest about 10-15 minutes before slicing. Delicious, always a big hit!!

  23. Nancy

    This recipe sounds great! I bought a boneless leg of lamb on sale this week, and am going to cook it this way over charcoal this weekend.

    One bit of advice for others who, like me, do not care for really sweet foods, and have therefore ruled out the mint jelly – try a vinegar-based mint sauce instead. Crosse & Blackwell makes one that is readily available in most supermarkets – and I’m sure there are several recipes available if you’d rather make your own. What I like about the mint sauce over the jelly is that you get the wonderful mint flavor added to your lamb without the (in my opinion, anyway) overwhelming sweetness of the jelly. Experiment with it by keeping the mint sauce separate, and just sprinkling some on a fork-full of lamb to see what you think of it. If you do, I’m pretty sure you’ll find yourself happily sprinkling the rest of the lamb on your plate with the mint sauce.

    Have a great Labor Day weekend, everybody!

    That’s great advice, thanks Nancy! ~Elise

  24. Cindy

    Yummy. The best lamb recipe ever! This is our family’s “go to” recipe. We have shared it many times with friends and family. Thanks for sharing! I just might make one this weekend!

  25. Goldiegal

    As an English woman, I was raised on the most wonderful lamb; roasted lamb, stewed lamb, braised lamb … you name it! I do take issue over your statement that lamb shoud not be cooked more than medium rare, though. If cooked gently it can be well done without being dry and/or tough. I prefer my meat well done and would certainly not put up with dry, unappetizing meat. “Well done” when “done well” means using patience.

  26. genghisbahng

    Hi — this looks amazing and I’m planning on making this tonight. Other recipes I’ve seen have called for making small cuts in the lamb with a paring knife before marinating. Sounds good, but also like it might allow the meat to dry out? Any thoughts on that? It goes without saying, love the site, have eaten my way through half of it already, and am looking forward to the rest. :)

    I haven’t tried this with lamb, but with pork or beef roasts we make small cuts and insert garlic cloves into the cuts. Turns out beautifully. ~Elise

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