Prime Rib Roast

Prep Time
3 hours
Cook Time
8 hours 30 minutes


  • 4 lbs. boneless prime rib
  • 2 tbsp salt
  • 1 tbsp pepper
  • 1 cup butter, softened
  • 7 garlic cloves, minced
  • 2 tbsp fresh rosemary, finely chopped
  • 2 tbsp fresh thyme, finely chopped
  • 1 large onion, chopped
  • 1 tsp olive oil
  • 2 tbsp flour


  1. Season the prime rib with salt and pepper then wrap in plastic wrap or tin foil. Place the prime rib into the refrigerator and allow it to sit overnight.
  2. Remove the prime rib from the refrigerator and allow it to come to room temperature.
  3. Mix together the butter, garlic, fresh herbs, salt, and pepper in a large bowl until evenly combined.
  4. Rub the herb butter mixture over the prime rib, being sure to evenly coat the entire surface.
  5. Preheat olive oil in the inner pot using the Sauté-then-Simmer® function. Once heated, sauté the onion for 12 minutes or until soft and browned.
  6. Place the prime rib into the inner pot with the onions and set the cooker on the Slow Cook function for 8 hours.
  7. When 8 hours has passed, remove the prime rib from the inner pot and place on a serving plate.
  8. In a small bowl, whisk together water and flour until there are no lumps. Mix in the flour mixture to the sauce still in the inner pot to thicken. Once thickened, coat the prime rib with the remaining sauce.