How to Roast a Leg of Lamb on the BBQ

Lamb is in season at the moment in the UK - and what better way to roast a beautiful, sustainable piece of pasture-fed British lamb, than on the BBQ?

If you've got quality charcoal, and a BBQ with a lid, and vents to control the airflow in & out, then you've got everything you need. So watch our video guide below where I show you how to roast a leg of lamb on the BBQ - and I promise it'll be the best lamb you've ever eaten!

If you haven't got time to watch the whole video, you can jump to the chapters below:

00:00 Introduction

00:06 The marinade

01:48 Barbecue & fuel

02:20 Setting up the barbecue

03:59 Using vents to control the temperature

06:17 What internal temperature to aim for

06:30 Pulling the lamb off the BBQ

06:42 How long to rest the lamb for

06:58 Slicing into the finished lamb

I used a 2.5kg rolled leg of lamb, but this would also work brilliantly with a bone-in leg of lamb.

We love this Spanish style marinade for lamb as a nice alternative to a more traditional Sunday roast.

My marinade for a 2.5kg joint used the following quantities:

• 100ml rapeseed oil
• 2 teaspoons smoked paprika
• 1 teaspoon cayenne
• 1 teaspoon cumin
• 2 teaspoons salt
• 1 teaspoon red wine vinegar
• Few fresh sage leaves, roughly chopped
• Small bunch parsley, roughly chopped including stalks 
• Few springs of thyme, stripped from stems and left whole
• 3 cloves of garlic, peeled & minced or finely chopped

Cooking indirect on your BBQ is essentially the process of turning it into an oven.

Traditional BBQing uses charcoal as a direct heat source - grilling food directly over your lit charcoal.

Indirect cooking keeps the heat source and the food apart, and using a lid allows for the circulation of hot air throughout the BBQ - convection cooking, just like a home oven.

Indirect cooking allows you to cook through large joints like leg of lamb evenly, and without charring or burning.

Before I started cooking outside, no-one had ever explained to me the importance of cooking to temperature. We're used to switching on an oven, and following the timing we find on the packet or online. Cooking to temperature is now the only way I cook!

We've all eaten dry chicken and tough steak and I think in the UK, we default to thinking we've bought bad meat - but the truth is, food cooked to temperature will always be safe as well as staying juicy and delicious!

In the UK lamb can be eaten rare, which is once it hits an internal temperature of 52°C. Check safety recommendations in your own country if you're watching this elsewhere. We like our lamb medium rare to medium, which we personally feel is around 65°C, as we don't feel the texture of lamb suits being cooked any less. For medium rare I would pull at 55-57°C, for medium I would pull at 65°C, and in both cases the lamb will continue to rise in temperature during the rest.

It took me a little while to trust this process, but once you've tried it out, you'll never go back! If you have any doubts, just leave your temperature probe in during the rest and watch the degrees tick up.

When using the snake method as per this video, it's really important to use the highest quality charcoal.

Lumpwood charcoal has lots of uneven surfaces, so when you arrange it in a snake, it doesn't have that many contact points. So as the fire progresses round the snake, it would be easy for the fire to die out unless the fuel is high quality and super easy to light.

British charcoal is class-leading in its ease of lighting for a couple of reasons. Firstly, the carbon content of British charcoal is much higher than that of factory produced charcoal, due to both the method of production it and the small batch approach with no compromise on quality. Secondly, as British hardwood trees are fast growing, our charcoal doesn't have the density of charcoal produced from Amazonian or African hardwoods, which also ensures easy and consistent lighting.

In any scenario where you're allowing unlit charcoal to light during cooking, it's also critically important to know that your charcoal contains no chemical binders or surface treatments. Many imported charcoals contain accelerants to help with lighting, and this sort of product shouldn't be used with the method of cooking in my video.

We don't always use smoking chunks when cooking indirect on the BBQ.

Good quality charcoal shouldn't impart a strong flavour on your food, just a very subtle wood smoke profile from the incredibly small amount of uncarbonised wood contained in the charcoal.

To add a smoky flavour to your food, you need to add wood chunks to your charcoal. When roasting such as this video, wood chunks will impart a noticeable but subtle smoke flavour.

To achieve deep smoky flavours, you should smoke at lower temperatures and for longer - better suited to fattier cuts of meat, such as lamb shoulder or beef short ribs.

Smoking chunks are easier to use than smoking chips, which take lots of topping up and therefore risk lowering the temperature of your BBQ.

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