A Successful Standing Rib Roast
Room Temperature: To cook evenly, the roast must not be cold - This time can vary depending on how big or small your roast is. I can't give you an exact time on this. If you don't let the roast come to room temperature, it will take longer to cook your roast, your roast won't cook evenly, and you'll end up with well-done slices on the end and raw meat in the center. Use your best judgment on room temperature times! I think that anywhere from 20 minutes to 45 minutes depending on the size of the roast, should work.
Sear the rib roast (prime rib) for 15 minutes at the higher oven temperature (450 degrees F.), then turn the oven to the lower temperature (325 degrees F.) for the rest of the cooking time. Do Not Cover the roast.
About 45 minutes before the estimated end of the roasting (bake) time, begin checking the internal temperature. Be sure to use a good instant-read digital meat thermometer. Play it safe and start checking early, as you don't want anything to go wrong.
NOTE: If you ignore every other bit of advice I've given, please pay attention to this: For a perfectly cooked rib roast, invest in a good meat thermometer. Internal temperature, not time, is the best test for doneness and you don't want to blow this meal!
When checking the temperature of your prime rib roast you should insert the meat thermometer so the tip is in thickest part of beef.
It should not be resting in fat or touching bone.
Cook until rib roast reaches an internal temperature of 120 degrees F. or your desired temperature.
Remove from oven, cover loosely with aluminum foil, and let sit approximately 15 to 20 minutes.
Cutting into the meat too early will cause a significant loss of juice. Do not skip the resting stage.
Approximate Weight| Oven Temperature| Total Estimated Time| Only Meat Thermometer Reading|
2 ribs - 4 to 5 pounds| 450 deg/325 deg F| 60 to 70 minutes| 120 degrees F
3 ribs - 7 to 8.5 pounds| 450 deg/325 deg F| 1 1/2 to 1 3/4 hours| 120 degrees F
4 ribs - 9 to 10.5 pounds| 450 deg/325 deg F| 1 3/4 to 2 1/4 hours| 120 degrees F
5 ribs - 11 to 13.5 pounds| 450 deg/325 deg F| 2 1/4 to 2 3/4 hours| 120 degrees F
6 ribs - 14 to 16 pounds| 450 deg/325 deg F| 3 to 3 1/4 hours| 120 degrees F
7 ribs - 16 to 18.5 pounds| 450 deg/325 deg F| 3 1/4 to 4 hours| 120 degrees F