Prime rib roasts are famous for their good quality. They are easier to prepare than a turkey on Thanksgiving morning. Prime rib roasts require minimal amounts of seasonings and can be cooked in a cooking bag for easy cleanup. Cooking bags are also great for keeping the roast moist as it cooks.
Set your prime rib roast out on your counter 2 hours before you plan to cook it.
When you're ready to cook, preheat your oven to 176 degrees C.
In a small bowl, combine 2 teaspoons of salt, 1 teaspoon of pepper, 1 teaspoon of oregano and 1 teaspoon of garlic powder.
Rub this mixture all over your prime rib roast.
Place the seasoned prime rib roast in a cooking bag and tie shut. Make sure the fat side is facing up.
Place the cooking bag in your roasting pan and put it in the preheated oven.
Cook for 45 minutes and then reduce the oven temperature to 107 degrees C.
Cook an additional 3 hours for a small roast, 3 1/2 hours for a medium roast or 4 hours for a large roast.
Remove from the oven and let sit for 20 minutes before serving.
The inside temperature of your roast should be 62.8 degrees C. Use a meat thermometer to check that the temperature is correct before eating.