© Paula Trites
A Prime Rib Roast is a cut of beef meant for roasting. It is cut from the most desirable part of the rib cage of a cow.
It’s a misconception that “Prime Rib Roast” refers to a roast with 7 rib bones in it. It will generally have at least 3 rib bones in it, up to a maximum of 7. It’s also a misconception that the “prime” in its name refers to the United States Department of Agriculture (USDA) top grade of beef. Which is obvious, if you happen to know that the same cut is sold in Canada and also referred to as Prime Rib Roast (and no, it doesn’t refer to the Canada Prime grade north of the border.)
What its name means is that it is cut from the prime or best section of the ribs, meaning somewhere between ribs 6 and 12 (anything lower than 6 is in the tougher, chuck section.) Other people feel that even going as low as rib 6 is even a bit iffy: that rib 6 can be included in a rib roast, but not in a Prime Rib Roast.
Any part of the roast that comes from the ribs closer to 12 will be even more tender, as the short loin, the most tender section of the cow, starts at rib 13.
Count on about 2 servings per rib.
Dry roast in oven at 350 F (180 C), allowing about 18 minutes per pound for medium-rare, 20 minutes for medium and 24 minutes for well-done. Using an instant-read meat thermometer, cook to 145 F (63 C) for medium-rare, 160 F (71 C) for medium, and 170 F (77 C) for well-done. When cooked to the point that you want it, remove from oven and let the meat rest, covered for about 15 minutes before slicing and serving; for a Rib Roast of 4 or 5 ribs, let rest for 30 minutes, covered.
Delmonico’s Restaurant in New York was using the term Prime Rib in 1894, to mean cut from the choicest section of the rib cage. The US only drew up tentative meat grading standards in 1916, and formalized them in 1927.