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Roast Butterflied Leg of Grass Fed Lamb

Roast Butterflied Leg of Grass Fed Lamb

Garth Brown |

Roast Butterflied Leg of Grass Fed Lamb

A Classic Preparation for a Smaller Leg of Lamb

Though I have grass fed in the title, this recipe should work fine with any lamb. But grass fed lambs are generally smaller than their grain fed counterparts. This translates to smaller cuts, which can be difficult to adapt to standard recipes. This recipe, for example, works great with a 2.5-4 pound butterflied leg of lamb, which is pretty typical in the grass fed world.

I also want to do away with some misconceptions. Grass fed lamb should not be tougher than grain fed, and grass fed lamb should still have a healthy amount of fat. It should not be excessively lean or excessively tough! The same rules that apply to grass fed beef are true of grass fed lamb.

A Great Meal in a Single Dish

I like dishes that are practical, which means consolidating when possible. If the side and the main course can be cooked simultaneously, as the root vegetables and lamb are here, it saves both prep and cleanup time. In this case it also means the same olive oil, rosemary, and garlic that season the lamb – as well as the lamb itself – season the potatoes and carrots, which only adds to their deliciousness.

Speaking of potatoes and carrots, while these are the classic choices, feel free to use parsnips, turnips, or whatever else you have on hand. A coarsely chopped onion never hurt anyone.

How To Cook

It seems I am physically incapable of writing a recipe without suggesting the use of a good digital thermometer. I love the ones from Thermoworks, a company that should probably have me on the payroll for how often I recommend their products. When cooking meat, it’s incredibly useful to know the exact temperature.

But I’m aware not everyone has one on hand. While a thermometer is convenient, the lack of one is not an insurmountable problem. After all, people have cooked for eons without them. So if you don’t have a thermometer, my advice is to simply cut into whatever you’re cooking. When it looks a shade less done than you like it, pull it from the oven. It will continue to cook a little on the counter as the residual heat moves from the outside in. This is far more effective than guessing based on time.

For whatever reason, though I like steak and beef roasts quite rare, I like lamb, especially leg of lamb, cooked a bit closer to medium. The ideal, in my opinion, is to pull it from the oven when it’s a bit over 135, which means it will finish at a temperature of around 140.

More Tips

Though this recipe is written to be cooked immediately, if you have time you can salt the meat in the refrigerator up to a day ahead. This lets the salt penetrate the leg of lamb, which keeps it a bit moister and evens out the seasoning. It’s not critical, but go for it if you’re so inclined. As far as seasonings go, while I like the classic combination of garlic, rosemary, and olive oil, use whatever herbs you have at hand.

I mention it in the recipe, but the exact time the root vegetables take to cook may vary. They might be done when the lamb is, but they might take a bit longer. If they need more time, while the lamb is resting, spread them out into an even layer, cover the pan with foil, and return it to the oven for as long as needed.

Cut the roast into quarter inch thick slices, put some potatoes on the side, and serve with a salad. Enjoy!

Roast Butterflied Leg of Grass Fed Lamb

A perfect roast leg of lamb, seasoned with rosemary and garlic, cooked with potatoes and carrots.
Course Main Course
Cuisine American
Keyword lamb
Prep Time 20 minutes
Cook Time 2 hours
resting time 20 minutes
Total Time 2 hours 40 minutes
Servings 4


  • 1 butterflied leg of lamb grass fed, 2½-3½ lbs
  • 3 tbsp extra virgin olive oil
  • 2 medium garlic cloves
  • 1 sprig of rosemary
  • lbs waxy potatoes
  • ½ lbs carrots
  • salt to taste


  • Preheat oven to 300°. Mince garlic and rosemary, then combine with two tablespoons of olive oil in a bowl. Set aside. Put one tablespoon of olive oil in the bottom of a baking dish, 9×13 minimum.
  • Peel potatoes and carrots, and cut them into chunks. Put the leg of lamb in the baking dish, then arrange potatoes and carrots around it. Sprinkle salt and pepper over the lamb and vegetables, then pour oil/garlic/rosemary blend over the lamb.
  • Roast until lamb reaches preferred doneness, 1-2 hours. (See note!)
  • Once leg of lamb is cooked, set it aside on a platter and cover it with foil. If the carrots and potatoes are not completely cooked, cover the baking pan with foil and return it to the oven for another 25 minutes. Regardless, let the leg of lamb rest a minimum of 20 minutes.
  • Slice the lamb thin and serve with roast vegetables.


•A thermometer is the best way to know when a cut of meat is done. Because a leg of lamb can vary so much in size and shape, as well as starting and oven temperatures, it is impossible to reliably cook one by time. If you do not have a thermometer you can always cut it open to take a peek inside.
•While I cook steak and most beef roasts rare, with a target finished temperature of under 130º, I prefer lamb closer to medium. I will pull it from the oven when the internal temperature reaches 137°, which means it will rise to about 140° while resting. But you should cook it as you prefer!

1 comment

This was my first time cooking lamb. It was a success! I cooked mine about an hour before I checked it and the temp was too high, but it was still tasty and not dry. I put the potatoes back in and cranked the oven up to 400 for about 20 more minutes. Even my three kids gobbled it all up.

Meredith ,

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