Even if you choose a "ready-to-eat" ham, you still need to bring it up to temperature. The only safe way to do this is by doing it slowly. Set your oven to 325 degrees and cook your "ready to eat" ham for ten minutes per pound, until it reaches 145 degrees internally. "Ready-to-cook" hams need to cook for about 20 minutes per pound and be brought to an internal 160 degrees. This means that a standard 8 lb. ham will need to cook for at least 2 hours and 40 minutes.