Things You'll Need
Few cuts of meat are quite as savory as prime rib when cooked to juicy perfection. As the name implies, this prime cut comes at a prime price, making an oven meat probe thermometer helpful for cooking it to the precise temperature to retain juices. An oven meat probe thermometer stays in the meat while cooking, connected to a small screen by a heatproof cord. The U.S. Department of Agriculture recommends an internal temperature of 145 degrees Fahrenheit for beef, which equals medium done-ness, but prime rib is commonly cooked to medium rare, or about 130 F.
Season the prime rib as desired and place it in a roasting pan. Preheat the oven to approximately 300 F to cook the prime rib slowly inside without overcooking the exterior.
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Set the oven meat probe thermometer to the desired internal temperature to which you wish to cook the prime rib, or a few degrees cooler, to account for the additional temperature rise after removing it from the oven. Exact instructions for temperature settings vary among different models, but most have a digital screen with fairly easy setup.
Place the prime rib roasting pan on the center rack of your oven. Insert the meat probe in the center of the thickest part of the roast. Close the oven door on the cord.
Set the digital screen part of the thermometer on the counter beside the oven while the prime rib cooks. Depending on the model, there's usually a reading for the set temperature, and the actual temperature inside the meat, so you can easily monitor progress. An alarm usually sounds when the meat reaches the target temperature. Expect to roast the prime rib for 20 to 25 minutes per pound to achieve medium rare or medium done-ness in a 300 F oven. Adjust cook times if you use a different oven temperature.
Remove the pan from the oven when the prime rib reaches the target temperature. Take the probe out of the meat and wash it thoroughly. Transfer the roast to a serving platter and allow it to rest for 3 minutes before carving so the juices inside the meat can redistribute.
If desired, you can remove the prime rib when it's about 20 degrees away from its target temperature, preheat the oven to its highest setting and cook the prime rib the rest of the way at the high temperature. This ensures a dark brown crust on the outside, which is desirable for prime rib.
As a general rule, beef is rare at 120 F to 125 F, medium rare at 130 F to 140 F, medium at 145 F to 150 F and well done at 155 F to 165 F. Prime rib is most commonly prepared to a medium rare or medium result so it retains much of its juices and remains tender.
Meat thermometers rarely give a perfect reading, so test the probe in boiling water to calibrate the thermometer. The thermometer should read 212 F -- the temperature of boiling water -- so adjust the setting for the prime rib done-ness to compensate for a reading over or under that temperature.