Roast Leg of Lamb

Ronan Killeen -

Some butchers will debone and roll the meat from a leg of lamb, or sell half legs, but I prefer to cook the entire piece of meat on the bone. The part of the bone that is bare can be used as a neat handle to turn the meat, using appropriate protection, of course.

If you try roasting large pieces of meat outdoors, you really need to have a quick read thermometer handy; it is the best way to be sure that the meat is cooked evenly and as rare or well done as you desire.

Dry Rub

This dry rub consists of a mix of spices and dried or fresh herbs. The main ingredients to call out are garlic, rosemary, salt and black pepper.

  • black pepper, ground, about 1 tablespoon
  • cumin seed
  • garlic powder
  • onion salt
  • Celtic course sea salt
  • Fresh rosemary, thyme and chives
  • Dried tarragon and parsley

Preparation

Lamb usually has a layer of fat covering part of the meat. This can be thick in places depending on the age of the lamb. Spring lamb, which lambs three months old or less, will have less fat. The dry rub will not really penetrate the fat, so the joint needs a little preparation before rubbing on.

With a sharp knife, cut slits in the fatty tissue all the way through to the meat layer below. I usually cut strips of about an inch thick. These thin strips will help the fat to render evenly and get nice and crispy.

You can apply the dry rub directly onto the lamb, but I usually apply some olive oil or melted butter onto the lamb first to make the dry rub stick on a little easier.

Make sure to rub right into the cuts in the fat and all over any exposed, meaty areas. Leave aside while preparing the barbecue.

Cooking

I always get asked how long will it take to cook (usually by my wife who is trying to assemble the rest of a dinner). But the answer is always “it depends”. There are a lot of factors to deal with. Be prepared to leave it cooking for up to two hours and also leave a little time for the meat to rest.

Like all slow charring cooks, a leg of lamb must be cooked over indirect heat. Light the coals and arrange them so that there is enough space for the leg to not be over the coals. I usually place them at one side of my kettle barbecue.

Place a drip try on the charcoal grate and pour in some water. This will help to keep the air moist inside the barbecue and will catch any fatty drips that spill off the joint of meat, protecting your barbecue.

The meat should be placed on the cooking grill over the drip tray. I usually place the fatty side facing up to start with the thickest part of the joint away from the coals. On my barbecue the far edge is where the hottest temperature is, due to the convection currents within the barbecue.

Place some pre-soaked wood chips on some tin foil over the heat or if you have a smoking box, use that. Place the cover on the barbecue and sit back and relax – the hard work is over!

I have a decent remote thermometer that gives a decent reading of the temperature inside the kettle. By manipulating the vents, I can get the temperature to about 180˚C and keep it throughout the cook.

For best results, turn the meat three or four times while cooking. Every twenty minutes should be good enough. Doing it too often will cause you to lose too much heat. Keep an eye on the coals; for longer cooks it is sometimes necessary to top up with more charcoal.

After about ninety minutes you can use the probe thermometer to take a reading. Stick in deep into the flesh trying to avoid the bone. Take readings in more than one spot to be sure that the meat is cooked evenly. It is more important to get everything to a minimum temperature than to worry about over-cooking part of the meat.

I try to cook to medium, which is about 60˚C  (that’s 140˚F). Add five degrees for well or subtract five for rare. Taste varies from culture to culture so experiment to fine what suits you. Err on the side of overcooked if you are preparing a meal for a large group. Near the bone, the meat will be rarer so it should be possible to find meat for all tastes.

For best results, leave the lamb to rest for ten to twenty minutes, covered by a layer or two of loose tin foil to stop too much heat evaporating. Sometimes I close the vents on the barbecue so that the temperature drops to about 80˚C. This will allow the meat to rest but keep the temperature at a safe level where bacteria cannot survive.

Slice into thin strips including a little of the fatty layer in each. Enjoy!