For a standard oven‑roasted leg of lamb, the usual guideline is about 20–30 minutes per 500 g (about 1 lb) at roughly 180–190°C (350–375°F), depending on how pink you like it, but always go by internal temperature for safety and accuracy.

Key timings and temperatures

  • For medium/“perfectly pink” lamb:
    • Around 25 minutes per 500 g at about 180–190°C.
* Internal temperature roughly 55–60°C (130–140°F) when checked with an instant‑read thermometer at the thickest part, avoiding the bone.
  • For well‑done lamb:
    • Around 30 minutes per 500 g at similar oven temperatures.
* Internal temperature around 70–75°C (155–165°F).
  • Many supermarket guides (like Waitrose and Australian lamb boards) give “minutes per 500 g plus extra minutes” formulas, but they all stress checking with a thermometer rather than time alone.

Typical example: 2 kg leg

  • Oven around 180–190°C.
  • Total roasting time:
    • Medium/pink: about 1 hour–1 hour 20 minutes.
* Well‑done: about 1 hour 30 minutes or a bit more.
  • Rest the lamb, loosely covered with foil, for at least 20–30 minutes before carving so the juices redistribute and the meat stays moist.

Quick reference table

Doneness Oven temp Guideline time Target internal temp
Medium (pink) 180–190°C ≈25 min per 500 g ≈55–60°C
Well done 180–190°C ≈30 min per 500 g ≈70–75°C
Slow, falling‑apart ≈160–170°C or lower Up to 40–45 min per 500 g ≈90°C or very tender to probe
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Practical tips

  • Bring the lamb closer to room temperature for 30–60 minutes before roasting so it cooks more evenly.
  • Use a thermometer rather than relying only on time; large, bone‑in joints vary a lot in shape and fat content, which affects cooking time.
  • Let the meat rest; it will rise a few degrees as it rests and become more tender and juicy.

Information gathered from public forums or data available on the internet and portrayed here.