It depends on the size of your ham and the temperature you are cooking. For example, an 8-pound ham will take about 3 - 3.5 hours at 250 degrees F; Or about 15 minutes per pound in the pellet grill. Essentially, you're reheating an already cooked hunk of meat, so you are going for warm enough to serve, not food safety, which is about 140 degrees F with a digital thermometer.