Great question. That all depends on the doneness and whether it is fresh or frozen. If the pork tenderloin is fresh, it will take 1 hour and 30 minutes. If it is frozen, it takes 2 hours and 15 minutes. Then determine the level of doneness you desire: Soft and Rosy: Cook at 131 degrees Pink and Juicy: (my favorite) Cook at 136 degrees Tender and Blushing: Cooks at 144 degrees Springy and Barely Pink: Cooks at 149 degrees Firm and Fibrous: Cook at 158 degrees