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How To Cook A Small Prime Rib Roast

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Cooking a full-sized prime rib roast can be a commitment due to its size and the effort it takes to prepare. Luckily, you don’t have to reserve cooking it for special occasions as you can also very easily cook a small one.

So, how to cook a small prime rib roast? The best way to cook a small prime rib roast is using the closed-oven technique where it is cooked at high heat for a short period of time so the exterior will develop a flavorful, brown crust, then left inside the turned-off oven for 2 hours to get the internal temperature to the desired doneness.

Read on for a detailed guide on how to cook the best small prime rib roast and the different cooking times and temperatures for the different sizes.

What Is A Prime Rib Roast?

Prime rib refers to a classic roast beef preparation that comes from the beef rib primal cut.

It is usually roasted with the bone in and served with a simple sauce made from au jus, the meat’s natural juices.

The word “prime” in prime rib roast indicates that the beef has been graded so by the USDA. If it is not labelled as “prime,” it is a standing rib roast, and if it is boneless, it is called a ribeye roast.

What gives prime rib roast this designation is the age of the cow from which the meat is taken and the amount of fat in the edible sections of the meat.

Prime rib is tender, moist, and flavorful, and the intramuscular fat (a.k.a. marbling) is what gives it its flavor and juiciness. The more marbling, the higher the grade the meat will get!

In reference to the age of the cow, it must be between 9-30 months of age to be considered prime.

What Size Of Prime Rib Should You Buy?

A full-sized prime rib consists of 7 ribs and is close to 15 pounds. It is enough to feed around 14 people, or even more depending on their appetites.

If you wish to serve fewer people and do not want to deal with the huge amount of leftovers, you can make a small prime rib roast that is both quicker and easier to prepare.

A small prime rib roast can weigh anywhere between 2-8 pounds, with the smallest size good enough to serve as little as 2 people with a few leftovers. Who minds leftover prime rib sandwiches, right?

A reasonable estimate of how much prime rib roast to prepare is 1/3-1/2 pound per serving. Depending on your and your guests’ appetites, you may assume a bit more or less.

How To Cook A Small Prime Rib Roast

Raw Grass Fed Prime Rib Meat with Herbs and Spices.

The closed-oven method is the best technique to cook a small prime rib roast weighing from 4-8 pounds.

It produces a perfectly medium-rare interior and a gorgeous brown crust on the outside.

The key to cooking a perfect prime rib roast with this method is knowing the exact weight of the roast. Make sure to note it down before you throw away the butcher paper it came in!

A great thing about this method is that you don’t need a meat thermometer, although you can use one if you want. 

You’ll also notice that there is no resting time, which might come as a surprise for those used to resting their prime ribs after cooking. You can skip the resting time with this method as the meat is basically resting as it sits in the oven.

It is also important to note that some oven models have cooling fans used to quickly reduce the temperature of the oven. 

Since the closed-oven method uses the residual heat from the turned-off oven to cook the prime rib roast, an oven with cooling fans may not be suitable.

If your oven has this feature, we recommend you use the traditional method for cooking prime rib roast instead of the closed-oven method.

Closed-Oven Method For Cooking A Small Prime Rib Roast

Here are step-by-step instructions for cooking a small prime rib roast using the closed-oven method:

  1. The night before cooking, unwrap the prime rib roast and let it sit uncovered in the refrigerator. This will dry out the surface and give it a nice brown color when roasted.
  2. At 3 hours before cooking, take the roast out of the fridge and place it on a sheet pan at room temperature.
  3. At 30 minutes before roasting, preheat the oven to 500°F and generously season the meat with kosher salt and freshly ground black pepper.
  4. Do the calculation for the cooking time, which we will discuss in a bit.
  5. When the oven is ready, set the roast, fat-side up, in a roasting pan with a rack.
  6. If you are unsure and nervous about the cooking time, you may insert a meat thermometer into the deepest part of the meat.
  7. Place the meat in the preheated oven and roast it for the time calculated above.
  8. When the time is up, turn off the oven and walk away. Do not open the oven door!
  9. After 2 hours, take the prime rib roast out of the oven, carve it, and serve it right away.
  10. If you used a meat thermometer, you will see that the internal temperature will be 130°F – the perfect medium-rare.

Approximate Cooking Time For A Small Prime Rib Roast

To determine the total “active” cooking time for the roast at 500°F, you need to multiply the weight of the roast (in pounds) by 5 minutes.

For example, if your roast weighs 4 pounds, multiply 4 by 5 to get the “active” roasting time, which will be 20 minutes. For a 4.5-pound roast, multiply 4.5 by 5, which would be approximately 23 minutes.

The time also depends on the level of doneness you are aiming for. The internal temperature of a rare roast will be different than that of a medium-rare one, which would ultimately result in shorter or longer cooking times.

How To Make Prime Rib Au Jus?

Au Jus (pronounced oh-ZHOO), is a simple sauce served with prime rib roast. It is thinner than gravy and has a very concentrated flavor. It is actually prepared using the roast’s juices coupled with aromatic vegetables.

Assuming you have just cooked a prime rib roast (using the traditional method), you will use the meat juices and the little toasty bits at the bottom of the roasting pan to make this delicious sauce.

Here are step-by-step instructions for making au jus to serve with your prime rib roast:

  1. Remove the roast from the roasting pan and pour most of the leftover fat into a jar. You may refrigerate it to use later to add a rich and meaty flavor to soups, stocks, and pasta.
  2. Place the roasting pan on the stovetop and add some chopped carrots, onion, and celery.
  3. Cook on high flame for 1 minute, stirring everything using a wooden spoon until the veggies start to brown and most of the liquid has evaporated. Be careful to not burn anything.
  4. Add in about 1.5 cups of beef stock and let it cook over high heat for another minute.
  5. Scrape all the toasty bits from the bottom of the pan using a wooden spoon.
  6. Transfer everything into a large saucepan with 1.5 cups of additional beef stock.
  7. Let it simmer for about 20 minutes or until the liquid is reduced by about 1/3.
  8. Strain the liquid using a sieve.
  9. For a finer strain, you may line the sieve with cheesecloth.
  10. Let it rest for a couple of minutes so that you can remove any fat that rises to the top.
  11. Add salt and pepper to taste.
  12. Serve warm with prime rib roast. Enjoy!

Mistakes To Avoid When Cooking Prime Rib Roast

Prime rib is an expensive piece of meat that is usually prepared on special occasions — regardless of the size and cooking technique, you wouldn’t want to spoil it!

Here are some of these most common mistakes to watch out for.

Cooking The Roast Cold

Cooking cold meat is one of the biggest mistakes you can make when cooking. Chilled meat will need more time to cook and will be exposed to heat for a longer time, resulting in the outer layer of the meat being overcooked.

With prime rib cuts, particularly big ones, this mistake is amplified by their size as the extra weight takes much longer to reach the desired internal temperature.

With the closed-oven method, a cold prime rib will interfere with the weight-to-cooking time ratio, and with the traditional method, you’ll simply end up with an overcooked roast.

The solution is to let your prime rib come to room temperature before roasting it. The bigger the roast, the more time it will need to stay at room temperature.

Seasoning It Too Early

Seasoning a prime rib is important, but doing so the night before or so is not the best idea.

The reason is that the longer the salt sits on the surface of the meat, the more liquid it will absorb and the less moist your meat will end up being, which is not something you want.

Keeping that in mind, the best time to season your prime rib is at some point when you leave it out at room temperature before roasting.

It may also be useful to know that no amount of seasonings, regardless of how long you keep them on, will penetrate beyond 2 millimeters into the roast, especially the bigger ones. 

Poking Holes Into The Prime Rib

The best way to measure the doneness of a prime rib is to use a meat thermometer. The issue arises when it is poked too often, resulting in too many holes on the roast that cause delicious juices to leak out.

The best way to use a meat thermometer when roasting a prime rib is to insert it into the meat and leave it in while it cooks. When the thermometer shows your target internal temperature, your roast is ready.

This way, you will have cooked your prime rib roast to perfection without turning it into a pincushion. For a small roast, you may use the closed-oven method that doesn’t require a meat thermometer at all.

What Can You Serve With Prime Rib Roast?

Prime rib

Prime rib roast is a delicious dish mostly served during the holidays.

You can prepare it according to your preference and serve it with your choice of side dishes.

Here are some delicious side dishes to serve with prime rib roast:

  • Roasted vegetables
  • Mashed potatoes
  • Garlic butter mushrooms
  • Cheesy baked asparagus
  • Twice-baked potatoes
  • Roasted broccolini
  • Potatoes au gratin
  • Creamy horseradish sauce
  • Creamed spinach
  • Mushroom risotto
  • Yorkshire pudding

What Can You Do With Prime Rib Leftovers?

When cooking prime rib roast, there are almost always leftovers. What can you do with them? How can you use leftover prime rib roast?

From sandwiches to nachos and pasta, the options are endless! Here are some of the best ways to use leftover prime rib roast:

  • Open-faced prime rib sandwiches
  • Prime rib beef stroganoff
  • Beef barley soup with leftover prime rib
  • Prime rib quesadillas
  • Leftover prime rib chili
  • Penne pasta with leftover prime rib
  • Prime rib tacos

How To Store Prime Rib Roast

If you are not preparing the prime rib roast right away, you can keep it in the refrigerator for 3-5 days. For long-term storage, it is best to store it in the freezer where it should stay good for 6 months to a year. 

Just make sure that it is wrapped properly to prevent any air or moisture from coming in contact with the meat — air is the enemy of frozen foods and causes them to dry out due to freezer burn!

Cooked prime rib is best eaten right away. But if you have leftovers that you need to store, you can keep them in the refrigerator for 5-7 days, or in the freezer for up to 6 months.

You may even store the roast whole, and if there is any leftover au jus, drizzle it on top of the roast to keep the meat nice and moist!

Related Questions

Now that you know how to cook a small prime rib roast and some of the most common mistakes to avoid, here are a few additional questions we thought you might have.

What is the difference between prime rib and ribeye?

Both prime rib and ribeye come from the same primal cut of beef. The difference in their flavors comes from the way they are cooked.

Prime ribs are roasted whole at a high temperature followed by low heat. Ribeye is cut into individual slices and grilled quickly over high heat.

Why is my prime rib tough?

A prime rib roast is best cooked rare or medium rare. If it exceeds the internal temperature of 140°F, all the fat will come out of the meat leaving it tough, dry, and chewy.

If you prefer medium, medium-well, or well-done meat, we suggest you consider other meat cuts.

What is the difference between bone-in and boneless prime rib roast?

Prime rib is available in both bone-in and boneless varieties. The bone insulates the meat and keeps it from drying out and overcooking, while a boneless rib roast is much easier to carve and quicker to cook.

To get the best of both, ask your butcher to remove the bones and tie them to the back of the roast. Simply untie and remove the bones after cooking and before carving.

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