Roast Leg of Lamb

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The most important thing to remember about cooking a lamb roast is to not over-cook it. Lamb has such wonderful flavor on its own, and is so naturally tender, that it is bound to turn out well, as long as it is still a little pink inside.

There is some debate over which method yields the best results—slow cooking at low heat the entire time, or searing first on high heat and then slow cooking. James Beard in his American Cookery prefers the slow-cook-low-heat method (he rubs the roast with salt and pepper and cooks it at 325°F the whole time.)

We generally get great results with the searing method, starting at high heat and then dropping the temp which is the method described in the following recipe. If you use searing method, you will have ends that are more well done, and as you get closer to the interior, more rare. This way you have a variety to serve to guests.

Another point where there are wildly varying opinions is the internal temperature that constitutes “medium rare”. I’ve seen references that range from 120° to 145°F. For this roast, I pulled it out at 125°F. As it rested the internal temperature continued to rise a few points as the meat continued to cook.

Roast Leg of Lamb

We like lamb on the rare side of medium rare, and this roast was perfectly done to our taste. Clearly an accurate meat thermometer is essential, and it helps to insert the meat thermometer at different places into the deep interior of the roast to get a good read.

A great way to keep tabs on how well the roast is cooking is to use a remote thermometer. This way you can tell when the roast is done without having to open the oven door, avoiding the loss of heat that comes from doing that.

These directions assume that you have let the roast sit at room temperature for an hour or two before roasting. If you are taking a roast and cooking it directly from the fridge, it will take longer to cook.

Updated from the recipe archive, first posted 2006.

Roast Leg of Lamb Recipe

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  • Prep time:
  • Cook time: 1 hour, 30 minutes
  • Marinating time: 2 hours
  • Yield: Serves 8 to 10

The marinade we used on this roast comes from my friend Suzanne and it works quite well. A simpler marinade of rosemary, olive oil, garlic, pepper, and lemon juice would do the trick quite nicely too. One can also make tiny slices into the surface of the roast and insert slivers of garlic and herbs.

Ingredients

Marinade

  • 1/2 cup orange juice
  • 1 cup white wine
  • 3 cloves garlic, minced
  • 2 teaspoons of fresh thyme or 1 teaspoon of dried thyme
  • 2 Tbsp of fresh chopped rosemary or 1 Tbsp of dried rosemary
  • 1/4 teaspoon of fresh ground pepper

Blend marinade ingredients in a blender, just a few pulses until well mixed.

Lamb Roast

  • One 6-pound leg of lamb, bone-in or boneless. (If boneless, the leg should be tied up with kitchen string by butcher.)
  • Marinade
  • Salt and freshly ground black pepper

Method

1 Marinate lamb: Place lamb and marinade into a plastic bag. Squeeze out as much of the air as possible from the bag and seal. Wrap again with another plastic bag to ensure that the marinating lamb doesn't leak.

Marinate for several hours, or overnight, in the refrigerator.

Remove the lamb, still in its marinade bag, from the refrigerator at least an hour (preferably two hours) before putting in the oven to help bring the lamb closer to room temperature before roasting.

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2 Preheat oven and arrange racks: Preheat oven to 425°F. Arrange two racks in the oven - a middle rack to hold the lamb, and a lower rack to hold a roasting pan with which to catch the drippings.

Note that this arrangement of racks and pans, with the roast sitting directly on the oven rack, will create a natural convection of heat in the oven, causing the roast to cook more quickly than if cooked the traditional method in a rack in a roasting pan.

3 Season lamb and place in oven: Remove the lamb roast from its marinade bag (you may want to temporarily place lamb in another roasting pan, just to make it less messy to work with.) Pat dry the marinade off the lamb with paper towels.

Generously salt and pepper all sides of the roast. Arrange the roast fattiest side up, so while the lamb is cooking the fat will melt into the meat.

Place the roast directly on middle rack of the oven, with a roasting pan on a separate rack a rung lower, to catch the drippings. You may also want to put some water in the bottom roasting pan, so that the drippings fall into the water instead of burning in the hot pan and smoking up your kitchen.

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4 Roast: Roast at 425°F for 20 minutes. Then reduce the heat to 300°F and roast an additional 40 minutes (for a 6 pound boneless roast) to an hour (for a 6 pound bone-in roast).  If you are cooking a roast bone-in, the bone will act as an insulator and will require a longer cooking time than a boneless roast.

In general estimate 10-13 minutes per pound for total cooking time (for rare), including that first 20 minutes at high heat. (Assuming you let the roast sit out for an hour or two before putting it in the oven. If it's right out of the fridge, it will take longer to cook.)

Note that the method of cooking directly on the oven rack will mimic a convection oven and the cooking time/oven temp needed will be less than you would need if you cooked the roast on a rack in a roasting pan. If you are cooking the roast directly in a roasting pan, rack or not, start the roast at 450°F and after 20 minutes reduce the heat to 325°F.

Also, the shape of the roast will have an impact on the cooking time. Our roast was rather long and thin, so it cooked up fairly quickly. A thicker roast may take longer than expected.

So, use a meat thermometer!

About 20 minutes before you expect the roast to be done, start checking the meat thermometer. Note that every time you open the oven door, you'll need 10 minutes or so to bring the oven back up to temperature, thus slowing down the cooking process. So, don't check too often, or use a remote meat thermometer. Remove the roast from the oven anywhere from 125°F to 135°F for medium rare. Lamb should never be cooked until well done or it will be too dry.

5 Let rest: Let stand for 25-30 minutes before carving (so the juices don't all run out when you cut into it). Cut away the kitchen string and slice with a sharp carving knife, 1/2 inch thick slices, against the grain of the meat.

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6 Collect drippings for gravy or sauce: While the roast is resting, use a metal spatula to scrape up the drippings in the roasting pan. Use the drippings to make a gravy, or use just the drippings themselves to serve with the lamb.

Serve with some mint chimichurri or homemade mint jelly.

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Links:

James Beard's Roast Leg of Lamb Recipe from Epicurious

ChefAlarm by ThermoWorks - we recommend this remote meat thermometer

Thermapen - another excellent thermometer, a favorite with chefs

 

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Showing 4 of 59 Comments

  • Herb

    This past Easter, my wife suggested we try something different than what we’ve had every year.
    So, we got a whole leg of lamb, bone-in. I watched a video online for how to bone it out, and I did it perfectly on my first try.
    You have to make sure you get the musk glands out of it as you bone it. There are 2 of them, so make sure you get both of them.
    If not, you are in for some nasty leg of lamb.
    Anyway, I boned it out, cooked it in the oven with some Moroccan spices, and it turned out to be our new go to Easter meal from now on. The sweet spices are very aromatic, and the warm spices add a depth of flavor you should not miss.

    I did not marinate it in anything other than liberal amounts of EVOO, and salt, black pepper, rosemary, and thyme.
    I cooked it with cinnamon, turmeric, nutmeg, a small pinch of cloves, and some Sriracha sauce mixed together.
    The results were outstanding & our guests were asking for my recipe.
    We will be having this again soon.

    Thanks for all the great recipes Elise.

  • Cole

    So we are going to have real chef advice/criticism here. I am sure there is a chef that works for this website or consults on things or whatever. The leg of lamb in the picture is on the medium side of medium rare and to be honest it’s just plain medium haha. However i’m sure if you follow this recipe and insert a thermometer in the outer center of the meat it will turn out how you like it. Probably just a tiny error and they went with it for the picture, no biggie. To be honest go ahead and bring that lamb out at 120 degrees and let it rest and it would be fine. You could probably cook it to a 115 internal temp and let it rest and it would work it’s way up close to 120. Different sizes will vary but I think 5 degrees internally is a fairly accurate reading of the carry over heating this size of cut will do. Cooking instructions absolutely right. The one they mentioned at 325 the whole time is outdated and I think they know that. Go ahead and get the outside seared/crusted/basted off. The outside will crisp up because it has a fat cap, and that fat will drip over the meat throughout the cooking process and just make things tasty. Haha I was bored. And thank you website for not putting an awful mint jelly or something with this. Who the hell eats mint jelly that’s under 85? If you like mint jelly sorry i’m not putting you down necessarily, but this is something that came about for meats that were pretty much spoiled or rotten before refrigeration. For whatever reason it just hung on through the years, at mostly bad restaurants. Pretty nice looking crust on the lamb even though its not quite even. Lol i’ll stop.

  • Whitney

    If I am going to cook two 6 pound boneless legs of lamb can I cook them into he same oven following this recipe?

  • Stacy Sissons McKenna

    I’m cooking a bone-in leg of lamb (12.6 lbs) for my friends – any idea on how to cook this? everything I see is for boneless (not an option at this point). My friends and I have been reminiscing about leg of lamb that we used to have for Easter. My mom used to make it and unfortunately she has passed and I have no clue!

  • Savita @ ChefDeHome

    Elise, yet again, an awesome recipe! I loved the pictures.

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