How to Cook a Leg of Lamb (Times, Temperatures & Butcher Tips)
A leg of lamb is one of the best “proper dinner” centrepieces — simple to cook, brilliant for leftovers, and perfect for a family roast. This guide covers everything you need: how much to buy, how to season it, cooking times per kg, internal temperatures, resting, carving, and leftover ideas.
How much leg of lamb do I need?
A good rule of thumb:
- 200–250g per person (boneless)
- 250–300g per person (bone-in)
If you want generous portions and leftovers, go toward the higher end.
The easiest (and best) seasoning for leg of lamb
Keep it classic — lamb doesn’t need much.
Simple lamb rub:
- Salt + black pepper
- 2–4 cloves garlic (crushed)
- Rosemary (fresh if possible)
- Olive oil
- Optional: lemon zest or a squeeze of lemon
Butcher tip: Score the fat lightly (don’t go deep), then push little slivers of garlic/rosemary into a few cuts for extra flavour.
Oven temperatures: what to use
You’ve got two reliable approaches:
Option A: Classic roast (best all-round)
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Start hot to colour, then finish at a moderate temperature
Option B: Low and slow (best for very tender lamb)
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Lower oven temp, longer cook, very forgiving
Leg of lamb cooking time per kg (easy guide)
These times are for roasting in the oven. Always finish by checking the internal temperature (next section), because ovens vary.
Classic roast method (recommended)
- Start at 220°C (200°C fan) for 20 minutes
- Reduce to 180°C (160°C fan) for the remaining time:
Per 1kg (after the first 20 minutes):
- Rare: 40 minutes per kg
- Medium: 50 minutes per kg
- Well done: 60 minutes per kg
Example: 2kg leg, medium
20 minutes high heat + (2 × 50 = 100 minutes) = about 2 hours total, then rest.
Internal temperature chart (the most accurate way)
Use a thermometer in the thickest part (not touching bone).
- Rare: 50–52°C (rests up to ~54–55°C)
- Medium: 58–60°C (rests up to ~62–63°C)
- Well done: 65–70°C+
Resting matters: the temperature rises after you take it out, and the meat stays juicier.
Resting (don’t skip this)
Rest your lamb 20–30 minutes.
How:
- Put it on a board
- Loosely cover with foil
- Don’t wrap tightly (you’ll soften the crust)
How to carve a leg of lamb
- Find the direction of the grain (the lines in the meat)
- Slice across the grain for tenderness
- If bone-in, carve along the bone first, then slice the larger muscles
Quick tip: If you want easier carving, ask your butcher to bone and roll the leg.
What to serve with roast lamb (spring-friendly ideas)
- New potatoes (crushed with butter + salt)
- Peas / spring greens / roasted carrots
- Mint yoghurt (yoghurt + mint + pinch of salt + lemon)
- Simple gravy from the roasting juices
Leftover ideas (the best part)
- Lamb and mint mayo sandwiches
- Lamb wraps with yoghurt + salad
- Shepherd’s pie
- Lamb fried rice / stir-fry
- Slow-simmered lamb broth (from the bone)
FAQ
How long do I cook a leg of lamb per kg?
After an initial 20 minutes at high heat, roast at a moderate temp for roughly 40 mins/kg (rare), 50 mins/kg (medium), 60 mins/kg (well done) — then rest.
What temperature should leg of lamb be when cooked?
Aim for 50–52°C rare, 58–60°C medium, 65°C+ well done, measured in the thickest part.
Do I cover leg of lamb with foil when roasting?
Not usually. Roast uncovered for better browning, then rest loosely covered with foil afterwards.
Why is my lamb tough?
Usually it’s overcooked or not rested (or carved with the grain). Use a thermometer and rest 20–30 minutes.
Shop leg of lamb online
If you’re ordering your roast for the weekend, you can choose your delivery date at checkout and get it delivered chilled and ready to cook.
Related guides
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Lamb shoulder vs leg (coming soon)
