How to roast a leg of lamb

Whether it’s a Sunday roast, a Friday night dinner party or a mid-week slow cook, a roast leg of lamb is a delicious and versatile joint of meat that will wow your dinner guests with minimal effort.

Our expert guide to cooking roast lamb covers everything from how long to cook your meat, what size leg to buy and how much lamb you’ll need per person, and the herbs and spices that will enhance its flavour, making sure your leg of lamb is the star of the show.

Make sure to also check our guide to the best frozen roast potatoes, and top-rated gravy granules - based on our independent consumer taste tests.

 How to roast a leg of lamb

Here's a basic step-by-step guide to roasting lamb:

1. Take the lamb out of the fridge for at least an hour before cooking so it can warm up to room temperature.
2. Set the oven to: 220°C/200°C fan/gas 7
3. Weigh your lamb to calculate the correct cooking time – it’s approximately 20 minutes per 450g/lb, plus an extra 20 minutes if you like it medium. 
4. Drizzle with olive oil and rub all over, before seasoning generously with salt and pepper.
5. Place the lamb into a roasting pan and put into the preheated oven.
6. Cook for 20 minutes before turning the oven down to 190°C/170°C fan/gas 5 and continuing to cook the lamb until it’s done.
7. Take it out of the oven, loosely cover it with foil and let it rest for around 15-20 minutes before carving and serving. 

Leg of lamb cooking times  

Once you know the weight of your leg of lamb, you can work out roughly how long it will take to cook it. The total cooking times for a leg of lamb (medium done) are as follows:

• 750g – 1 hour 5 minutes 
• 1kg – 1 hour 15 minutes 
• 1.5kg – 1 hour 40 minutes
• 2kg – 2 hours 5 minutes
• 2.25kg – 2 hours 30 minutes 
• 2.50kg – 2 hours 50 minutes
• 2.75kg – 3 hours 

If you prefer it well done, you can alter the cooking times to 30 minutes per 450g/lb, plus an extra 30 minutes.

Make sure you also check the cooking times listed on the packaging, or ask the butcher if you’re not buying from a supermarket.  

Cooking times can also vary depending on how well your oven sticks to its temperature. When we've tested ovens, we've found that some overheat by 30ºC more than the temperature you set on the dial – enough to turn a perfectly tender joint of lamb into a crispy mess. 

If you're looking to replace your oven, find one that will cook accurately and evenly with our built-in oven, freestanding cooker and range cooker reviews. 

What size leg of lamb do I need to buy?

If you’re trying to calculate how much lamb you’ll need to cook, a good rule of thumb is 400g + 200g per person. The list below will give you an idea of roughly what weight of lamb you'll need to feed everyone around your dinner table.

• 750g – 1kg serves two people 
• 1kg – 1.5kg serves four people 
• 1.5kg – 2kg serves six people
• 2.25kg – 2.75kg serves eight people 

Do you like a side of Yorkshire puddings with your lamb? See how to make Yorkshire puddings. 

What to add to a leg of lamb?

While a well-cooked leg of lamb will taste fantastic on its own, fresh herbs and the right accompaniments can add a delicious depth of flavour to your plate. 

Here are some of the best herbs, spices, sauces, and condiments to pair with your lamb: 

• Rosemary – the classic combination. Stud the sprigs into the meat before cooking or add to a marinade or butter.
• Garlic – slather in a garlic butter or stud garlic cloves into the meat before cooking. 
• Black pepper – create a mustard and black pepper crust, pair with a black pepper sauce or simply season with black pepper before roasting. 
• Cumin – cover your lamb with cumin (ground or seeds) before cooking to create a crust. 
• Curry powder or Baharat – can be used as a dry rub or mixed into stews or other wet dishes.
• Oregano – mixed with olive oil, garlic, salt, and pepper and rubbed over the meat before roasting.
• Thyme – you can simply add the thyme – stalks and all – into your pan when cooking. 
• Mint and mint sauce – pair your roast lamb with a mint sauce or jelly, sprinkle fresh mint leaves into a side salad, or make a mint marinade. 
• Mustard – rub English or wholegrain mustard into your lamb before roasting to leave a spicy crust.
• Yoghurt / Tzatziki – serve on the side, in a gyro or drizzled over your sliced lamb. 
• Curry sauce – lamb goes perfectly in a curry, particularly a Rogan Josh, Jalfrezi or Bhuna. 
• Gravy – use the juices from your roast lamb to make a homemade gravy.
• Chimichurri – made of finely chopped parsley, minced garlic, olive oil, oregano and red wine vinegar, fresh and vibrant chimichurri sauce can be served alongside lamb or used as a marinade before cooking. 
• Tomato relish – serve as a condiment with any lamb dish. 
• Gremolata – garnish with this tangy green sauce made up of chopped parsley, lemon zest, and garlic.
• Aioli – a creamy, garlic sauce that will taste best served with lamb and potatoes. 

Best red wines - serve your lamb with one of our top-rated picks for a perfect pairing.

How to slow roast a leg of lamb

To slow roast a leg of lamb, all you need to do is lower the heat and lengthen the cooking time. We also advise covering the lamb with foil to help the meat retain its moisture. 

1. Take the lamb out of the fridge for at least an hour before cooking so it can warm up to room temperature.
2. Set the oven to: 170°C/140°C fan/gas 3
3. Weigh your lamb to calculate the correct cooking time – add around three hours to the cooking times listed above. For example, 5-6 hours for a 2kg leg of lamb.
4. Drizzle with olive oil and rub all over, before seasoning generously with salt and pepper.
5. Place the lamb into a roasting pan, cover loosely with foil and put into the preheated oven.
6. Remove the foil 45 minutes before it’s done so the meat can brown. 
7. When the meat is cooked to your preference, take it out of the oven, loosely cover it with foil and let it rest for around 15-20 minutes before serving.

Alternatively, use one of our best slow cookers. 

More roast lamb recipes

Jamie Oliver's roast leg of lamb recipes 

Coined the best roast leg of lamb recipe, Jamie Oliver uses a marinade made up of rosemary, garlic, olive oil and lemon zest to flavour the lamb and advises cooking the joint on the hot bars in the oven rather than in a roasting pan. 

Another one of Jamie’s leg of lamb recipes swaps out the marinade for a herby butter and the hot bars for a traditional pan, filled with veg.

Nigella Lawson's roast leg of lamb recipes 

Like Jamie, Nigella also rubs her leg of lamb with a marinade. But this one features rosemary, oregano, lemon, orange, garlic, olive oil and salt, which once cooked will form a soft, fresh crust on the top of your joint. 

Nigella’s herbed leg of lamb recipe also advises cooking your lamb in half an inch of water. 

Mary Berry's roast leg of lamb recipes 

Mary’s crowd-pleasing, one-pot, slow roast leg of lamb recipe takes around 5 hours, so you’ll need to start earlier in the day. 

Seasoned with garlic, paprika and thyme, the lamb is then cooked with ratatouille-style vegetables and covered with foil to keep it moist. 

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