I have no clue. I'm suppose to make one for Christmas Eve dinner because my husband VOLUNTEERED me to do it. HELP! I'm having about 30 in laws coming! I'm going to Costco to buy the meat. What should the packaging say on it? Prime Rib? Rib Roast? What? Am I suppose to marinate it first? How long do I cook it for? I do, however, have a meat thermometer, that's something! And what else should I make to go with the meat? Vegetablewise.