How long to cook a 18 lb prime rib roast

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This Prime Rib Recipe is tender, juicy and delicious! Step-by-step tips for the best prime rib, makes the perfect standing rib roast to serve on holidays!

Prime rib is one of those dishes that takes center stage when you serve it. This salt and pepper crusted prime rib is so easy to make and always tender, juicy and delicious. I love to prepare my slow roasted prime rib throughout the holidays or when I am having a special, celebratory meal, especially at Christmas. It is so delicious and a meal that my whole family and guests always love.

It can also be a bit intimidating to make since prime rib is such a large rib roast, not to mention that it can be a rather expensive cut of meat. Luckily, with just a few simple tips, it is so easy to prepare!

What Cut of Meat is Prime Rib?

Prime rib roast, also known as standing rib roast, is the cut of beef from the back of the upper ribs portion of the cow. This cut comes from the same primal rib section of the cow that a rib eye steak does. To be considered a rib eye steak, the meat must be cut before the rib roast is cooked. Prime rib is a larger cut of meat that typically includes the bone.

The full cut prime rib is made up of seven ribs and will generally weigh from 16 to 18 pounds, and feeds about fourteen guests. 

How to Buy Prime Rib

When buying prime rib from the grocery store, you’ll want to make sure to ask the butcher for a standing rib roast and let them know how many people you will be serving. A quick way to determine the size that you need to purchase is generally, you will have two servings per bone, depending on the thickness you plan to serve. If serving as the main entree, generally a thicker cut is desired, if as part of a buffet, thinly carved pieces are usually fine.

I prefer to buy a bone-in prime rib, or standing rib roast, as the bones serve as a natural rack for the meat when baking, insulate the meat while cooking, and makes for a juicier more tender prime rib when cooked.

Ask the butcher to prep the meat for you by cutting away the bones from the bottom of the meat. But, do ask them to go ahead and tie the bones back onto the meat for you. This way, you have the benefit of cooking the beef with the bones for a tender prime rib while still being able to easily cut away the tied bones to make carving for serving easier.

Prep for the Most Tender Prime Rib

Salt. Besides the bones making for a juicy prime rib, using salt on the standing rib roast makes for the most tender meat. About four to five days before you plan to cook it, you’ll want to salt it. The salt when left on the meat for an extended period (from about an hour to days), seeps into the meat and provides for better seasoned, juicy meat. This is a dry brining method.

If for some reason you aren’t able to salt it that far in advance, do so at least an hour prior to roasting. Anything shorter than an hour will work against you and result in a tougher exterior to your meat.

Wrap and Refrigerate. Once you’ve salted the roast, wrap it tightly with plastic wrap and store it in the refrigerator until an hour prior to cooking.

Place on Roasting Pan. Remove your beef from the refrigerator an hour prior to cooking, then unwrap and place, bone side down, on a roasting pan fitted with a roasting rack, and allow to reach room temperature.

Season. At this point, add any additional seasonings you want to use. I like to serve it pepper encrusted for extra flair, but you can use a blend of herbs in garlic butter is also amazing. These optional seasonings are included below so you can use based on your preference.

How Long to Cook Prime Rib

The amount of time that you cook the beef depends on how well done you prefer your roast.

Preheat. Preheat your oven to 475º F for about 15 minutes.

Roast. Then roast for 15 minutes and then reduce to 325º until it reaches the desired internal temperature, usually about 11 – 12 minutes per pound for rare prime rib, 12 – 13 minutes for medium-rare prime rib, and 14 – 15 minutes for medium well prime rib.

Note that you’ll need to use an internal meat thermometer to ensure it’s cooked to the exact temperature you desire. You will also want to allow for any carryover cooking, meaning you’ll want to remove from the oven about 2-4 degrees less than the temperature you desire.

What Temperature Should I Roast the Prime Rib to Reach?

You will want to roast your prime rib until the meat thermometer registers the following:

• 115º F – 120º F for rare
• 125º F – 130º F for medium rare
• 135º F – 140º F for medium
• 145º F – 150º F for medium well

To roast your prime rib for medium rare, you will want to remove it from the oven when the temperature reaches 125º F and let it rest for about 20 to 30 minutes before slicing.

Allow it to rest about 20 minutes. This allows for the most tender, juicy prime rib! Then move to the carving board for slicing and serving.

Tip: Be sure to use a meat thermometer to make certain that the roast has reached the desired temperature. You will want to check various areas of the meat with the meat thermometer to be certain that you have cooked it perfectly. The worst thing is overcooking.

Serve at the Perfect Temperature

If your guests prefer a more well-done slice of beef, I normally have a rimmed roasting pan standing by to place the beef on and return to the oven for a few minutes to cook it to their desired temperature. That way, everyone is able to have their prime rib as they prefer it!

Store any Leftovers to Preserve Tenderness

If you have any remaining, (and that’s a major if!) you can easily save it for later serving. It is amazing with biscuits and a mustard or horsey sauce as an appetizer! You’ll be glad that you sliced your roast as you served it so that the meat is easier to reheat without losing any of the tenderness and juiciness you took such care to get!

What to Serve with Prime Rib

We love to serve our prime with a bit of Horseradish Sauce on the side. It is creamy and a bit spicy from the horseradish and goes perfectly with the beef! As side dishes, I love to serve Baked Potatoes or Twice Baked Potatoes. You just can’t go wrong with either of those! And for a salad, we always love my Apple Pear Salad with Pomegranate Dressing. If you are serving your standing rib roast throughout the holidays, you absolutely need to make Bart’s Cinnamon Rolls. They are perfection!

These recipes, along with others, are all included in my Make-Ahead Christmas Dinner Menu that I think you’ll love as well!

Seasoning Options

Herb and Garlic Prime Rib

Mix together 4 tablespoons softened butter, 2 tablespoons chopped fresh rosemary, 1 tablespoon fresh thyme and 4 large minced garlic cloves. Spread generously on the outside of the standing rib roast before cooking. Spoon the pan juices over the roast before serving.

Pepper Encrusted Prime Rib

Press 3 tablespoons of crushed black pepper onto the outside of the roast before cooking.

Coffee Encrusted Prime Rib

Mix together 2 tablespoons ground coffee, 1 teaspoon onion powder, 1 teaspoon garlic powder, and ¼ teaspoon cayenne. Spread generously on the outside of the standing rib roast before cooking. Spoon the pan juices over the roast before serving.

Here’s my Perfect Prime Rib recipe. I hope you enjoy it as much as we do!

Perfect Prime Rib Recipe

Dinner — 3 hrs

Prep Time 1 hr

Cook Time 2 hrs

Course Main Course

Cuisine American

Perfect Prime Rib Recipe – This Perfect Prime Rib Recipe is tender, juicy and delicious every time! Step-by-step tips for the best prime rib, perfect to serve on holidays, special occasions and more! 

• ▢ 1 (3 – 4 bone) bone-in prime rib, about (10 – 10.5 pounds)
• ▢ 1 tablespoon kosher salt
• ▢ 2 teaspoons freshly ground black pepper

• Salt prime rib from one hour to up to five days prior to cooking and serving your prime rib. Once salted, wrap tightly in plastic wrap and refrigerate until an hour prior to cooking.

• An hour prior to cooking, remove prime rib from refrigerator, unwrap and place, bone side down, on a roasting pan and allow to reach room temperature. If cooking a boneless roast, place onto a roasting rack inside the roasting pan. At this point add pepper or other seasonings, if using.

• Preheat oven to 475º F. Then, roast your prime rib for 15 minutes and reduce to 325º F until your prime rib reaches the desired internal temperature, usually 11 – 12 minutes per pound, about 1 hour and 50 minutes. Using an internal meat thermometer, remove your prime rib from the oven about 2 – 4 degrees less than the desired serving final temperature you desire.

  The temperature of the prime rib will continue to rise due to carryover cooking. Tent prime rib with foil and allow to rest for 20 minutes.

  Note: Here are the temperatures you'll allow to reach depending on the doneness desired:

  115º F – 120º F for rare

  125º F – 130º F for medium rare

  135º F – 140º F for medium

  145º F – 150º F for medium well

• Place on a carving board for slicing and serve.

Serving: 3ounces | Calories: 340kcal | Protein: 19g | Fat: 29g | Saturated Fat: 12g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 12g | Cholesterol: 72mg | Sodium: 55mg | Potassium: 258mg

Enjoy!
Robyn xo

From the Add a Pinch recipe archives. Originally published 2014.