How long to cook 8.5 lb prime rib

Make sure you know the proper prime rib cooking temperatures before trying to make this delicious cut of beef! The cooking temperature and internal temperature are important in making sure your prime rib is not over or undercooked, but just right!

Prime rib is one of those cuts of meat that you may think is difficult to cook. This is a common misconception because it is a higher-priced cut of meat and is mostly served on special occasions.

You don’t have to go to a restaurant for Sunday brunch to enjoy this delectable meat though. With a few simple tips, you can easily make an amazing prime rib at home for your next Easter brunch or another special occasion.

• The Ideal Doneness for Prime Rib
• Is it Safe to Eat Medium Rare Prime Rib?
• Do I Have to Serve Prime Rib Medium Rare?
• Table 1: Desired Doneness for Prime Rib
• What Temperature Do You Cook Prime Rib?
• How Long Do You Cook Prime Rib?
• How to Test If Your Prime Rib is Done
• Tips for Cooking the Best Prime Rib
• How to Prepare Prime Rib

The Ideal Doneness for Prime Rib

The important thing when cooking prime rib at home is to know the right temperature to cook it at, how long to cook it for, and what the desired level of doneness is. 

Typically, prime rib is considered best served medium-rare. When checking the internal temperature of the roast, you want it to be between 130-135°F (35-37°C).

Prime rib is one of those cuts of meat that you may think is difficult to cook. This is a common misconception because it is a higher-priced cut of meat and is mostly served on special occasions.

You don’t have to go to a restaurant for Sunday brunch to enjoy this delectable meat though. With a few simple tips, you can easily make an amazing prime rib at home for your next Easter brunch or another special occasion.

Is it Safe to Eat Medium Rare Prime Rib?

Technically, 130-135°F (35-37°C) is below the suggested internal temperature at which to consume meat. The USDA recommends that prime rib and other roasts be served at 145°F (63°C) or above to help prevent food born illnesses. While it is always important to keep this in mind, many chefs still safely serve prime rib at medium-rare.

When cooking any cut of meat that you intend to serve below medium it is recommended to purchase it from a reputable butcher. While it may be a bit more expensive than grabbing on in the grocery aisle, buying from a local butcher will give you the highest quality of meat (and you get to support local businesses in your area).

Do I Have to Serve Prime Rib Medium Rare?

While it is traditionally cooked to medium-rare, this is not a hard and fast rule. Many people prefer their prime rib to be just a bit more cooked throughout.

You are the one eating the prime rib; therefore, choose the desired level of doneness that you and your guests prefer. If you have a lot of varying tastes, cooking the prime rib to medium or medium-well will give options of doneness to serve: well done on the outer edges and medium in the center.

Use the recommendations below to determine what temperature your desired doneness is when cooking prime rib at home.

Table 1: Desired Doneness for Prime Rib

What Temperature Do You Cook Prime Rib?

Whether you decide on medium-rare or something a bit more well done, you can cook your prime rib in the same fashion and at the same temperature.

The ideal way to cook prime rib is by following a low and slow method. Some cooks prefer to cook their prime rib at a very low temperature of 250°F (120°C) for several hours. Many others prefer to cook at a little bit higher temperature so that it does not take quite as long to cook.

Cooking your prime rib at either 250°F (120°C), which is ideal for smoking a prime rib roast, or 325°F (160°C) will result in delicious prime rib. Choose what works best for the time you have and the size of the roast you are cooking.

How Long Do You Cook Prime Rib?

Temperature and time go hand in hand when cooking the perfect prime rib. Another important factor is the size of your roast.

In addition to these factors, you need to decide if you would like to brown your roast before lowering the temperature (this is great for sealing in the juices and getting a nicely crusted outside).

Before you follow the guidelines below, begin by preheating your oven to 450°F (230°C) Place your seasoned prime rib in a shallow roasting pan with the fat side down. Place the pan in the oven and sear the roast for 15 minutes. Then lower the temperature to either 250°F (120°C) or 325°F (160°C) and follow the guidelines below.

To determine how long you need to cook your prime rib, first identify how large the roast is. Then use the chart below to help you determine how long to cook your prime rib at either temperature.

How Long to Cook Prime Rib at 250°F (120°C)

Cook your prime at 250°F degrees for 25 minutes per pound of meat

How Long to Cook Prime Rib at 325°F (160°C)

Cook your prime rib for approximately 17-20 minutes per pound of meat. (This chart rounds the cooking time to approximately 17 minutes per/pound to help avoid overcooking).

Keep in mind that cooking times are approximations. Depending on your oven, you may need to cook the prime rib for a longer or shorter amount of time.

The times listed above are a good starting point though, so begin by following the guide. Then use your meat thermometer to test the internal temperature and adjust times as needed.

How to Test If Your Prime Rib is Done

Before you begin cooking your prime rib make sure that you have a meat thermometer on hand. If you don’t have one, you will want to buy one before cooking your prime rib.

With a large cut of meat like a prime rib, as well as one that you are working hard to get the exact right level of doneness, a meat thermometer is the best tool to use.

To test the meat, slowly pull it out of the oven. You can leave it on the oven rack if you would like, just be mindful of the hot rack.

Insert the meat thermometer into the thickest part of the roast and wait for the temperature to register.

Important Note on Testing Internal Temperature:

You want to pull your prime rib out of the oven before it reaches your desired temperature! For example, if you want a perfect medium rare prime rib at 130-135°F (35-37°C) you will want to stop cooking it when it reaches 120-125°F (49-52°C) on the thermometer.

When you pull the prime rib out, it will continue to cook for up to 30 minutes while it is resting. This is called carryover cooking.

Therefore, to make sure it doesn’t accidentally overcook once it’s out of the oven – take it out early.

Tips for Cooking the Best Prime Rib

• Remove your prime rib from the refrigerator an hour before cooking and let it sit on the counter. Allowing the meat to come to room temperature before cooking will allow for the prime rib to cook the most evenly throughout.
• Remove the prime rib from the oven when the internal temperature is 5-10 degrees less than what your desired doneness is.
• Remove the prime rib when it is finished cooking and let it sit (uncovered) to rest for 20-30 minutes before serving. This allows the meat to continue to cook internally and will give you the best taste and texture.

How to Prepare Prime Rib

The great thing about prime rib is that because it is such a high-quality cut of meat, you do not need to do a lot to get the most from it. Many cooks find that a simple seasoning of salt and pepper is perfect.

Just because it can be made with a simple seasoning, doesn’t mean you can’t enjoy adding some more flavor as well! Fresh garlic or herbs like rosemary can be amazing flavor additions to prime rib.

If you want a delightful and savory prime rib, try out my recipe for oven-roasted prime rib with prime rib rub.

If you are curious about how to smoke a prime rib, you can also try my recipe for smoked prime rib!

Angela @ BakeItWithLove.com

Angela is an at home chef that developed a passion for all things cooking and baking at a young age in her Grandma's kitchen. After many years in the food service industry, she now enjoys sharing all of her family favorite recipes and creating tasty dinner and amazing dessert recipes here at Bake It With Love!

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