Roasted bone in leg of lamb and homemade gravy

Weber Kettle Bone-In Leg of Lamb Roast 

Roast a bone-in leg of lamb on a Weber Kettle for perfect BBQ lamb with tender medium doneness and rich homemade gravy. Easy, reliable step-by-step method. With simple prep, high-heat roasting, and a long rest, you’ll get consistent results every time. Ideal for Sunday lunch or holidays, and surprisingly easy once you know the method.

A bone-in leg of lamb offers some of the best flavour thanks to the marrow and natural fat content. Ask your butcher for a leg with the fat cap still attached, but not excessively thick—too much exterior fat won’t render during roasting.

Make shallow criss-cross cuts (about 5mm / ¼ inch deep) across the fat and flesh to increase surface area for seasoning. This also lets the rub penetrate better without damaging the structure of the roast.

You’ll need a charcoal kettle BBQ (or any grill set up for indirect high heat), charcoal baskets, and some quality charcoal briquettes, a meat thermometer, and a roasting pan for the gravy base. Also having a sharp knife helps with carving up the roast.

Preparation:
Start with a 2–3kg (4.4–6.6 lb) bone-in leg of lamb. Trim only if there are thick, hard chunks of exterior fat that won’t render. Score the fat in a criss-cross pattern about 5mm (¼ inch) deep.

Mix the seasoning—salt, lemon pepper, rosemary, oregano, garlic powder, and onion powder. Rub olive oil over the lamb, then coat thoroughly with the seasoning, working it into the slits.

Prepare the gravy base by roughly chopping three onions (leave the skin on for deeper colour). These will sit under the lamb to catch drippings.

The Cook:
Set up your Weber Kettle for high-heat indirect cooking. Fill a chimney with briquettes, light it, and once ashed over, divide the hot fuel into two charcoal baskets on opposite sides of the grill. Place the pan of onions between them and add 3 cups of warm water.
Preheat the BBQ to around 220°C (428°F) with all vents open.
Place the lamb in the centre of the grill between the baskets and insert a meat probe into the thickest part. Cook with the lid vent positioned over one side of the lamb for the first hour. After an hour, rotate the lid 180° for even cooking.
Roast until the internal temperature reaches 59°C (138°F) (about 2 hours for a 2–3kg leg).

The Payoff:
Rest the lamb for 30 minutes under foil and a heavy towel. This is crucial—resting allows carryover cooking to bring the lamb to 63°C (145°F), the perfect medium doneness, and keeps the meat juicy.
To make the gravy, strain the onions and drippings into a saucepan and add beef stock and white wine. Reduce for 15 minutes. In a separate pan, melt butter and whisk in flour to form a brown roux. Stir this into the gravy to thicken. Season to taste.
Carve the lamb and serve with the rich, aromatic gravy.

Ingredients:
Main Ingredients
•    1 x bone-in leg of lamb, 2–3kg (4.4–6.6 lb)
•    2 tbsp olive oil

Seasoning
•    1 tbsp kosher salt
•    2 tbsp lemon pepper
•    1 tbsp dried rosemary
•    1 tbsp dried oregano
•    1 tbsp garlic powder
•    1 tbsp onion powder

Gravy
•    3 onions, roughly chopped (skins on)
•    750ml warm water (3 cups)
•    500ml beef stock (2 cups)
•    250ml white wine (1 cup)
•    30g unsalted butter (1 oz)
•    2 tbsp plain flour
•    Salt and pepper, to taste

Recipe Steps:
1    Score the Lamb:
Score the fat in a shallow criss-cross pattern about 5mm (¼ inch) deep.
2    Season the Lamb:
Mix all seasoning ingredients. Rub olive oil over the lamb, then apply the seasoning, working it into the cuts.
3    Prepare the Gravy Base:
Roughly chop onions (leave skins on) and place them in a roasting pan. Add 3 cups (750ml) warm water.
4    Set Up the BBQ:
Light a chimney of briquettes. Once ashed over, divide into two charcoal baskets on opposite sides of the grill. Place the pan of onions between them. Preheat the BBQ to 220°C (428°F).
5    Roast the Lamb:
Put the lamb on the grill between the baskets. Insert a temperature probe. Cook for 1 hour with the lid vent on one side of the lamb, then rotate the lid 180°. Continue cooking until internal temp reaches 59°C (138°F). Total cooking time: about 2 hours.
6    Rest:
Remove lamb and rest under foil and a towel for 30 minutes. Internal temperature should rise to about 63°C (145°F).
7    Make the Gravy:
Strain drippings and onions into a saucepan. Add beef stock and wine. Simmer 15 minutes to reduce. In another pan, melt butter and whisk in flour to form a roux. Add to the gravy and stir until thickened. Season to taste.
8    Serve:
Carve the lamb and serve with the homemade gravy.

Recipe Info
•    Prep Time: 15 minutes
•    Cook Time: 2 hours + 30 min rest
•    Serves: 6–8
•    Effort: Average
•    Course: Main
•    Cuisine: Australian
•    Hydration: 4 beers (optional… but recommended)

Tips & Variations:
•    Resting is non-negotiable: A long rest dramatically improves tenderness and juiciness.
•    Swap the rub: Lamb also works well with Middle Eastern rubs (cumin, paprika, coriander) or a garlic-mint blend.
•    Add herbs to the pan: A few rosemary sprigs in the gravy pan add extra aroma.
•    Charcoal alternative: You can cook this in a gas BBQ or oven—keep the temp around 220°C (428°F) and still use the onion pan for drippings.
•    Prefer medium-rare? Pull the lamb at 55°C (131°F) and rest to 60°C (140°F).

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