A probe thermometer is essential.

These instructions from Lawry's restaurant are excellent: YOU WOULD USE "NEXT DAT REHEATING"

REHEATING PRIME RIB
You’ll Need: Roasting Rack, Roasting Pan and Instant-Read Thermometer. If a roasting rack is not available,
the Prime Rib can be placed directly in a roasting pan.
SAME DAY REHEATING – please allow for at least 1 ½ hours before serving.
1. Preheat oven to 350°.
2. Remove the Prime Rib from plastic wrap and aluminum foil packaging and place in a roasting pan,
rib side down.
3. Insert a meat thermometer into the middle lengthwise of the Prime Rib, making sure to not to touch
the bones, and measure the internal temperature of the roast. This will give you an idea of how
long the roast will need to be in the oven.
 If 100˚ or below, cook for 15-20 minutes
 If 100˚ - 120˚, cook for 10-15 minutes
 If 121˚ or above, cook for 10 minutes
4. Check internal temperature after allotted time. The following temperatures correspond to the
meat’s doneness:
 130˚ = Rare center to medium well ends
 145˚ = Medium center to well done ends
 160˚ = Well done throughout
5. If the internal temperature is lower than your desired doneness, return the roast to the oven and
check the temperature every 10 minutes.
6. Once your desired temperature is reached, remove the roast from the oven and place on a cutting
board for carving. Loosely tent the Prime Rib with aluminum foil and let rest for at least 15-20
minutes before carving.

NEXT DAY REHEATING – please allow for at least 3 hours before serving.
NOTE: If you will not be enjoying your Prime Rib until the following day, remove the Prime Rib from
plastic wrap and aluminum foil packaging and place in a roasting pan, rib side down, uncovered. Allow
the Prime Rib to chill overnight in the refrigerator.
1. Preheat your oven to 350°.
2. Remove the Prime Rib from the refrigerator. Wrap the Prime Rib tightly in aluminum foil and place
on a roasting rack.
3. Place the Prime Rib in the oven and cook for 20 minutes. After 20 minutes, turn the temperature
down to 250° and continue to cook for 1 hour.
4. Remove the roast from the oven and remove and discard the aluminum foil. Insert a meat
thermometer into the middle lengthwise of the Prime Rib, making sure to not to touch the bones,
and measure the internal temperature of the roast. This will give you an idea of how long the roast
will need to be in the oven.