Rib Count

Approximate Weight

Oven Temperature

Total Estimated Time

Meat Thermometer Reading (Rare)

2 ribs

4  to 5 pounds

450°/325° F

60 to 70 minutes

  120° F     

3 ribs

7 to 8.5 pounds

450°/325° F

1 1/2 to 1 3/4 hours

  120° F     

4 ribs

9 to 10.5 pounds

450°/325° F

1 3/4 to 2 1/4 hours

   120° F     

5 ribs

11 to 13.5 pounds

450°/325° F

2 1/4 to 2 3/4 hours

   120° F     

6 ribs

14 to 16 pounds

450°/325° F

3 to 3 1/4 hours

   120° F     

7 ribs

16 to 18.5 pounds

450°/325° F

3 1/4 to 4 hours

Prime Rib Roast, at room temperature (very important)

2 tablespoons butter, room temperature

Trim roast of excess fat but not the thin layer of fat the butcher leaves on the roast to protect and baste it while it cooks. To cook evenly, the roast must not be cold—let it stand at room temperature for about 2 hours.

If your rib roast is frozen, let it thaw completely in the refrigerator. Remove the roast from the refrigerator about 2 hours before cooking, the longer time for the largest roast (if you don't let the roast come to room temperature, if will take longer to cook your roast).   

Pat the rib roast dry with a paper towel or napkin.

Preheat oven to 450°F. Smear the cut ends of the roast with the butter. Place the roast (ribs down or fat side up) in a heavy stainless-steel or other metal pan. (I do not recommend using a nonstick pans, as these pans yield fewer of the cooked-on bits that make the tasty juice.) The rib bones are a natural rack; you won't need a metal one.

Sear the rib roast for 15 minutes at the higher oven temperature (450°F), then turn the oven to the lower temperature (325° F) for the rest of the cooking time. Every 1/2 hour, baste the cut ends of the roast with the fat accumulated in the roasting pan.

About 1/2 hour before the estimated end of the roasting time, begin checking the internal temperature (use a good instant-read digital meat thermometer ). Insert meat thermometer so tip is in thickest part of beef, not resting in fat or touching bone. Cook until rib roast reaches an internal temperature of 120°F. Remove from oven, cover with aluminum foil, and let sit approximately 20 to 30  minutes. NOTE: Remember, the roast will continue to cook as it sets. The temperature will rise to 125 to 130° F internal temperature (medium rare).

NOTE:  To hold cooked roast until serving time, immediately turn off oven and leave door ajar after removing roast. Let roast sit 15 minutes on counter and then return roast to the oven, door closed, for up to an hour or even 2 hours for the biggest roasts. Check the temperature every 15 minutes. If will rise approximately 10° F at first, then gradually subside. 

To carve:  Using a long, thin, sharp knife, make one cut to slice off the chine or feather bones (the large end bones). Slice off steak-size pieces at the desired thickness.

Serve with side of Au Jus Juice and Horseradish Sauce (see recipe below).

NOTE:  Au Jus is a French term meaning "with juice." The term is used to describe the serving of meat, most often prime rib roast, surrounded in or served with a container of the natural juices that were produced as drippings while the meat was being cooked.

Horseradish Sauce :
1/4 to 1/2 cup prepared horseradish (according to your taste)
1 pint (2 cups) sour cream or creme fraiche
2 tablespoons fresh lemon juice
1 teaspoon salt

In a medium-sized bowl, combine horseradish, sour cream or creme fraiche, lemon juice, and salt; thoroughly mix. Refrigerate until ready to serve.

NOTE: Can be made 2 days in advance. Cover and refrigerate.

Makes approximately 2 1/2 cups.