Question: how long does it take to cook a prime rib on the grill?
Answer: Place the roast, fat side up, on the hot grate over the drip pan and cover the grill. Step 5: Grill the roast until cooked to taste, 3 1/2 to 4 hours for a medium-rate roast of this size, figuring on 12 to 14 minutes per pound. (If using a charcoal grill, you'll need to add 10 to 12 fresh coals to each side every hour.