Cooking time for Semi-boneless leg of lamb?

I have a semi boneless leg of lamb weighing 5 pounds.. I am marinating it in a yogurt-herb marinade over night for dinner tomorrow and i will b cooking it in the oven..( i kno, if i could get to my grill that is all bundled up for winter, i so would) I will be wiping off excess marinade b4 cooking and do want somewhat of a crusty char on top without over cooking it... anyone? Need time, temp and technique if u have one..and thank you!