For a leg of lamb, a good oven setting is Gas Mark 4 after an initial hot blast at Gas Mark 6–8. A common method is to start it hot for 20 minutes, then turn it down to Gas Mark 4 for the rest of the roast.

Simple guide

  • Initial heat: Gas Mark 6 to 8 for 20 minutes.
  • Main roast: Gas Mark 4 for medium roasting.
  • Alternative lower setting: Some guides use Gas Mark 3 for half or whole leg, especially at 170 C.
  • Resting: Let it rest 15 to 20 minutes before carving.

Timing

A practical rule for medium is about 15 to 25 minutes per 500 g, depending on the recipe and whether the leg is bone-in or boneless. For well done, add a bit more time.

Easiest answer

If you just want one number: Gas Mark 4 is the usual setting for roasting a leg of lamb after an initial high-heat start.