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 it in plastic wrap or tin foil. Place the prime rib in the refrigerator and allow it to sit overnight.
  2. Remove the prime rib from the refrigerator and let it come to room temperature.
  3. In a large bowl, mix together the softened butter, minced garlic, fresh rosemary, fresh thyme, salt, and pepper until well combined.
  4. Rub the herb butter mixture all over the surface of the prime rib, ensuring it is evenly coated.
  5. Preheat the olive oil in the inner pot using the Sauté-then-Simmer® function. Once heated, sauté the chopped onion for about 12 minutes or until softened and browned.
  6. Place the seasoned prime rib into the inner pot with the sautéed onions. Set the cooker on the Slow Cook function and cook for 8 hours.
  7. After 8 hours, carefully remove the cooked prime rib from the inner pot and place it on a serving plate.
  8. In a small bowl, whisk together water and flour until there are no lumps. Add the flour mixture to the sauce that remains in the inner pot to thicken it. Once the sauce is thickened, coat the prime rib with the sauce.
  9. Slice the prime rib and serve with the flavorful sauce.