Updated 30 September 2026
A butterflied leg of lamb is one of the best ways to cook a leg for a crowd. Taking the bone out and opening the meat into one flat piece means it cooks in well under an hour instead of two, it takes on a marinade beautifully, and it's just as good on the BBQ as in the oven. Butterflying isn't difficult with a sharp knife and a bit of patience. Here's how to do it at home, plus a marinade and roasting times.
Choosing the lamb
Start with a bone-in leg. Our Whole Carvery Leg of Lamb 2.2-2.7kg (£34.99) is a 2.2–2.7kg bone-in leg. It's sent frozen and arrives at least partly thawed; let it thaw completely in the fridge before you start. Once boned and butterflied, a leg this size loses some weight to the bone and will feed around 8–10 people.
How to butterfly a leg of lamb
You'll need a sharp, narrow boning knife (or a small, sharp cook's knife) and a board that won't slip.
- Find the bones. A leg has the aitch bone (part of the hip) at the wide end, the thigh bone in the middle and the shank bone at the narrow end. Feel for them with your fingers first.
- Remove the aitch bone. At the wide end, cut around the exposed hip bone, keeping the knife tight against it, and work it free at the ball-and-socket joint.
- Open up the thigh bone. Turn the leg so the meatier side is down. Make a long cut along the length of the thigh bone, right down to the bone.
- Cut the bone free. Keep the tip of your knife against the bone and scrape and cut around it, opening the meat out like a book. Cut through the knee joint and continue down the shank bone, then lift the bones out.
- Butterfly the thick parts. The meat will now be uneven. Where it's thick, cut horizontally into the muscle, stopping short of the edge, and fold it open like a page. Aim for an even thickness of about 4–5cm all over.
- Trim. Take off any thick pieces of hard fat and silvery sinew, but leave a thin layer of fat on the outside.
Keep the bones: roast them for stock or gravy. If you'd rather not bone it yourself, look at our boneless lamb joints in the legs of lamb collection.
Garlic, rosemary and lemon marinade
- 4 garlic cloves, crushed
- 2 tbsp chopped rosemary
- Finely grated zest and juice of 1 lemon
- 4 tbsp olive oil
- 1 tsp smoked paprika or ground cumin (optional)
- Black pepper
Score the meat lightly, rub the marinade all over, and leave it in the fridge for at least 2 hours, or overnight. Season with salt just before cooking. For more ideas, see our lamb seasoning guide. Middletons Garden Mint Glaze 110g (£1.99) also makes a quick finishing glaze.
Take the lamb out of the fridge 30–45 minutes before cooking.
Butterflied leg of lamb roasting times
These times are for a leg butterflied to about 4–5cm thick. Thinner pieces cook faster, so use a thermometer.
| Method | Temperature | Pink (medium-rare) | Medium |
|---|---|---|---|
| Oven | 220°C (200°C fan) | 25–35 minutes | 35–45 minutes |
| Sear, then oven | Sear, then 200°C | 20–30 minutes | 30–40 minutes |
| BBQ (lid on) | Medium-hot | 12–15 minutes a side | 15–20 minutes a side |
Temperatures in the thickest part: about 55–60°C for pink, 60–65°C for medium, and 70°C or more for well done. The temperature will rise a few degrees while the lamb rests. Whole cuts of lamb can be served pink; this is a whole muscle cut, so it's fine pink in the middle.
In the oven
- Heat the oven to 220°C (200°C fan, gas 7).
- Lay the lamb flat, skin-side up, in a roasting tin. You can put it on a bed of sliced onions and halved garlic bulbs.
- Roast for 25–35 minutes for pink, checking the thickest part with a thermometer.
- Rest, loosely covered with foil, for 15 minutes.
On the BBQ
A butterflied leg is made for the BBQ. Set up for two-zone cooking, with the coals on one side.
- Sear the lamb over the hot side for 3–4 minutes a side, until well browned.
- Move it to the cooler side, put the lid on, and cook for about 10–12 more minutes a side, until it reaches the temperature you want.
- Rest for 15 minutes.
Two metal skewers pushed through the meat in a cross shape make it much easier to turn.
Carving and serving
Because it's uneven, a butterflied leg will have some pinker and some more cooked parts, which suits a table of mixed tastes. Slice across the grain into thick slices. Serve with flatbreads, yoghurt and a crunchy salad, or go traditional with roast potatoes and homemade mint sauce. Leftovers are brilliant in wraps the next day.
More lamb guides
- How to cook a leg of lamb in the oven
- Roasting a whole carvery leg of lamb
- Lamb cuts and cooking guide
Browse legs of lamb and all lamb.
Butterflied leg of lamb FAQs
How long does a butterflied leg of lamb take to cook?
About 25–35 minutes at 220°C for pink, or 12–15 minutes a side on a lidded BBQ, for a leg about 4–5cm thick. Always rest it for 15 minutes.
What does butterflied mean?
The bone has been removed and the meat opened out flat, into a piece of roughly even thickness, so it cooks quickly and evenly.
Can you butterfly a leg of lamb yourself?
Yes. With a sharp boning knife, cut along the bones, lift them out and open the meat flat. Allow 15–20 minutes the first time.
What temperature should butterflied lamb be?
About 55–60°C in the thickest part for pink, and 60–65°C for medium. It will rise a few degrees as it rests.
How many people does a butterflied leg of lamb feed?
A 2.2–2.7kg bone-in leg, once butterflied, feeds roughly 8–10 people.