How Long Do You Cook A 10 5 Pound Prime Rib?
Cooking a 10.5-pound prime rib depends on the desired doneness. For rare, cook for about 2.25 to 2.5 hours at 325°F. For medium-rare, cook for about 2.5 to 2.75 hours. For medium, cook for about 2.75 to 3 hours. Always use a meat thermometer to ensure that the internal temperature is at least 125°F for rare, 135°F for medium-rare, and 145°F for medium.