Grilled Butterflied Leg of Lamb

Butterflied Grilled Leg of Lamb, butterflied for easy grilling, marinated in rosemary garlic marinade! Directions for grilling over charcoal or gas.

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Photography Credit: Elise Bauer

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.

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.

Grilled Marinated Leg of Lamb

Why use a butterflied the leg of lamb? A butterflied lamb roast is one that has the leg bone removed so that you can lay the roast out flat. You can do it yourself or have your butcher do it. Laying the roast flat on the grill helps it cook faster and more evenly.

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

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  • Prep time: 1 hour, 10 minutes
  • Cook time: 1 hour
  • Yield: Serves 8 to 10

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 Make the marinade: 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 Marinate the lamb: 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.

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.

5 Sear the lamb: 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.

6 Move to cool side of grill and finish cooking: 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).

7 Let rest before cutting: 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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Showing 4 of 26 Comments

  • naya

    Im making this recipe tonight for myself but I only have a half pound piece of butterflied lamb leg. i wanted to roast it in the oven but cant find how long should i let cook. any advice?

  • Sarah B

    This recipe (with your Mint Chimichurri) was a huge hit at our Easter dinner last night. Thank you SO much for the detailed instructions on grilling~my hubby was nervous to attempt (& potentially mess up) such a large, expensive cut of meat but it turned out beautifully. Such a blessing for us as nervous hosts of our first Easter lamb meal

  • Michelle Dold

    THANK YOU SO MUCH FOR THIS RECIPE GUIDE!! I followed this exactly and my first leg of lamb for this thanksgiving turned out AMAZING!!!

  • Madeline Scrogin

    I think I have too many years experience both cooking lamb roasts and eating roast lamb all across France (nothing to compare with the salt marsh raised lamb from the western coast of France, especially near St. Michel). I guess this might be the only advantage of ahem, aging! But I would never cook a roast or grilled leg of lamb without trimming the fat and most of the fell away.

    Also it should be noted that marinades might add flavor but they do not “tenderize” lamb. Good pink lamb comes already as tender as it’s ever going to be (go to a quality butcher or market). And only the cook can take that away, ending up with over-cooked dry and chewy lamb.

    Lamb fat does not have a good and so it won’t add a good flavor. The opposite might be more true.) The flavor of the lamb roast should come from the lovely pink tender flavor of the meat itself and so even flare-ups are better saved for beef.

  • sue ross

    My boneless leg of lamb is very thick on one side and thin on the other. Should I cook for short side med rare and cut that part off, grilling the thicker side more? I could also flatten the thicker side before cooking.

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