Let’s face it, with what full Prime Rib Roast costs these days, you can’t afford NOT to cook it perfectly. So don’t waste your time with other posts—here’s the simple truth: If you get the temperatures right, your prime rib will be spectacular. If you don’t get the temperatures right, it won’t. And who knows more about temperature than ThermoWorks? No one, that’s who.
Whether you like your prime rib bone-in, boneless, or with the bone cut off and tied back on… Whether you plan on smoking your prime rib, or oven-roasting… Whether you like it sliced thin with horseradish sauce and legumes, or slabbed with potatoes and gravy….
How you cook the meat itself is where all the glory is to be found. What you want is a crisp, savory crust on the outside with perfect, pink, edge-to-edge doneness inside (no unsightly gray band). Each of those things takes its own preparation. Here’s how to do it…
Prime Rib Doneness Temperature
Here’s the gist of the whole thing: prime rib roast has a pull temp of 125°F (52°C) in the coolest part of the prime rib roast for medium-rare doneness. That can vary a little with different cooking temperatures, but basically, if you get nothing else from this, remember that
HOW TO COOK A PRIME RIB AT A GLANCE
(Prep time: 3-5 hours)
- Trimming: Whether you’re roast is bone on or boneless, trim off any excess gristle or fat. You want as close to a round, aerodynamic shape as possible with a fat cap that is ¼ inch thick at the very most.
- Tying: Increase the aerodynamics and evenness of your prime rib by tying it with string in between each bone or, if boneless, every inch or so.
- Seasoning: Generously apply your favorite seasoning to all sides. We love just kosher salt and fresh ground black pepper.
- Chilling: Prepare your prime rib for searing by putting your tied prime rib into the freezer until it measures 30°F (-1°C) just below the surface.
- Searing: Straight from the freezer, sear your prime rib in a piping hot skillet (cast iron if you’ve got one) with a surface temp of 400°F (204°C) or more. Sear 2 ½ minutes on each side until a dark brown crust forms all around.
- Roasting (or smoking): Pre-heat your oven or smoker to 225°F (107°C). Place your seared prime rib on a rack on a backing sheet, to allow air to circulate below the meat.
- Verifying Doneness: Cook your Prime Rib Roast until the lowest internal temperature you can find with an instant-read thermometer is 125°F (52°C) for medium rare or 130°F (55°C) for medium doneness.
- Resting: Remove the roast from the oven. Loosely tent with foil and let it rest on the counter for 30 minutes. During this time the lowest internal temperature should rise to between 130 and 134°F (55-57°C) for medium rare or to between 135 and 140°F (58-60°C) for medium.
- Carving: Carve to desired thickness. If you carefully follow this method, you should have a deep brown, rich, savory crust with perfect, edge-to-edge pinkness inside.
- Bask in the praise from your friends and family.
HOW TO COOK A PRIME RIB IN DEPTH: EVERYTHING YOU NEED TO KNOW…
Part 1: Preparing Your Prime Rib Roast
How to Trim Your Prime Rib Roast:
The way you trim your prime rib roast will largely depend on whether you buy a bone-in or boneless rib roast.
Which one should you buy? The debate has gone on for years, with the pro-bones arguing that the bones contribute more flavor, and, if pressed, insisting that the marrow was seeping in from the bones to the meat. This has been shown by J. Kenji López-Alt , a team at Texas A&M’s Meat Science Department, and Meathead Goldwyn to be untrue. The marrow in the ribs is the wrong kind for “seeping” and the bones themselves are pretty impenetrable—even to the gooey, tasty kind of marrow.
But there is one way in which leaving the bone in can actually have an effect: as a heat buffer. Having a shield of bone and connective tissue on your meat can help to prevent overcooking. But if you like your roast rare to medium-rare, it can actually lead to chewy, undercooked meat right near the bone.
In the end, you’ll have to decide based on your preference. A standing rib roast (which can be as small as two bones or as long as the full seven) is beautiful to behold, but more difficult to carve—you will probably just cut the bones off to serve it anyway. Yes, a bone-in roast will usually be cheaper per pound, but you will be paying for bone weight, which is not directly useful to you.*
On the other hand, boneless prime rib roasts are easy to cook, easy to carve, but cost more per pound. The choice is yours, but in the ThermoWorks kitchen, we most often cook boneless roasts. Either way, you should spend a moment examining your roast with a knife in hand before roasting.
Trim off any gristle and any excess fat. A nice fat cap can enhance the mouthfeel of the Prime Rib but you don’t want more than ¼ inch of thickness.
If you go boneless, you have the option to trim off the flat part that extends away from the main muscle. We always do. This increases the aerodynamic shape of the roast which will help it cook more evenly. The flat part always overcooks anyway.
* If you choose to get a bone-in roast, we recommend having your butcher prepare it “cut and tied,” with the bones cut off and tied back onto the muscle. This creates an easy carving situation while maintaining presentation and heat-buffering advantages. The bones are fun and tasty to gnaw on after dinner, or you can use them to make a tremendous beef stock.
Tying Your Prime Rib Roast:
Tying a rib roast is very important. If you don’t know how to do it (YouTube will gladly teach you), have your butcher tie it for you. By tying the roast, you can create a more uniform shape and density along its length. This translates directly into more even cooking, with less chance of a gray ring around the inside edge of your holiday-table centerpiece. The tying also evens out the surface, allowing for better browning in the sear phase, and will result in a better-looking finished product that is easier to slice.
If you have a bone-in roast, tie between each of the bones and across the length of the roast. If you have a boneless roast, space your string every inch or so. Tie the strings taught to hold the roast as compact as possible.
How to Season Your Prime Rib Roast:
Prime rib doesn’t need a lot to dress it up, and will, in fact, do swimmingly with nothing but salt and pepper. Some people are tempted (especially if they are cooking their rib roast in a smoker) to put all kinds of powerful spice rubs on their rib roast. If you feel so inclined, that is your choice, though this meat really shines with classic flavors.
That being said, if you really want to dress it up and stay within a classic flavor palate, I recommend making a wet-rub of 3 cloves minced garlic, the minced leaves of 2 fresh rosemary sprigs, 1 teaspoon black pepper, 1.5 tablespoons dijon mustard, and 1/4 cup olive oil. Apply it after your sear but before it goes in the oven and you will be hailed as a luminary of the kitchen.
How to Pre-Rest Your Prime Rib Roast:
There is sadly no consensus on the appropriateness of a counter-rest phase in preparing a prime rib roast. For example, America’s Test Kitchen features three different methods for preparing a prime rib for roasting—1) salted in the refrigerator for 24 hours, 2) salted one hour in the refrigerator followed by pre-resting for two hours on the counter, and 3) just pre-resting for two hours on the counter. Other experts go straight to the oven without a pre-rest. While others suggest putting the prime rib in the freezer before searing, to chill the meat. All this ambiguity can be perplexing.
Here at ThermoWorks, we wanted to determine the effects of various thermal preparations prior to searing and cooking in a boneless prime rib roast. We roasted 5 boneless prime rib roasts, carefully monitoring the thermal state of each roast through our various stages of preparation, cooking, and resting. For two of the prime ribs, we rested the meat on the counter prior to searing and roasting. For three prime ribs, we placed the meat in the freezer prior to searing and roasting. We were curious to see which of these methods produced a finished result with the most desirable attributes of a finished prime rib—a crispy outer crust but with no discernible gray ring between the seared crust and the rosy pink meat inside!
We found that the best results came from seasoning the roast, then placing it in the freezer until the outside 1/4″ reached 30°F (-1°C), then moving right to the sear. This resulted in an almost undetectable gray ring on the roast.
SO, to properly prepare your Prime Rib Roast for searing without a resulting gray band, place a probe into the center of the roast just below the surface and set your ChefAlarm LOW alarm to 30°F (-1°C). Keep the roast in the freezer until the low alarm sounds.
* Note that this step will take approximately an hour in the freezer and will also add cooking time on the back end to bring the center of the meat back up from its chilled state before cooking. So, if you’re pressed for time, omit this step, but be prepared for a more pronounced gray, overcooked band of meat just below the crust.
Part 2: Cooking Your Prime Rib Roast
How to Sear Your Prime Rib Roast:
Searing is an important part of roasting a prime rib. Searing the roast first will kill the surface bacteria, which is a nice touch, especially when you are roasting at lower temperatures. However, searing is important from a culinary standpoint as well as a safety standpoint. We get a bit of a nice crisp-meat crust from the sear, but more importantly, we create a coating of Maillard-reaction browning all over the roast. This natural flavor enhancement will baste the meat during cooking with tastier juices than if we had put it in the oven raw.
To sear your roast, preheat your cast iron skillet to 500°F (260°C) as measured with an Industrial IR with Circle Laser (IRK-2) infrared thermometer. Remove your roast from the freezer and remove the probes immediately before searing. Sear the cold roast on all sides, giving each surface about 2.5 minutes against the pan, resulting in a “nicely browned” exterior.
How to Cook Your Prime Rib Roast:
Preheat your oven or smoker to 225°F (107°C).
Place the tip of your tracking thermometer probe into the center of the roast and set the target high temperature alarm to 125°F (52°C) on your ChefAlarm® for a perfectly pink medium-rare doneness. Because a prime rib Roast is such a large cut of meat, it will experience fairly significant Carryover Cooking (from 5-8°F [2-4°C] depending upon the size of the roast) while it rests. Your serving temperature should end up being around 130-134°F (55-57°C) throughout the roast which is just right!
Note that you really should cook such an expensive roast to Medium Rare to experience all of the beefy goodness you paid for. Normally, those who like a little darker brown on their portion (like the children in the room) can pull from the end slices. If you DO want to cook to medium, however, you can add an additional 5°F (2°C) or even—dare we say it—10°F (6°C) to your pull temp. That means pulling your roast near 130°F (55°C) or 135°F (58°C) and finishing after the rest with a final internal temperature 135-144°F (58-62°C).
How to Know When Your Prime Rib Roast is Done Cooking:
Using a leave-in probe thermometer like ChefAlarm® is important for making sure you don’t accidentally overshoot your target doneness temperature, but a probe that is not placed 100% correctly in the meat will also give you bad info about doneness. If the probe is too close to the surface, you’ll have colder meat deeper in the center. That’s why it’s important to also verify the doneness of the roast with an accurate instant-read thermometer like Thermapen® ONE.
When your ChefAlarm sounds, insert your Thermapen probe deep into the meat and pull it up slowly through the roast. Look for the lowest temperature you see. Meat is only as done as its least-done part! If you find a lower temperature than the one displayed on your leave-in thermometer, move the leave-in probe to the cooler spot and continue cooking. If you don’t find any lower temps, you’re good to move to the resting stage.
How to Rest Your Prime Rib Roast:
Once your roast reaches 125°F (52°C) and you verify its temperature with Thermapen ONE and remove it from the oven, cover it with aluminum foil to rest. All meats should be rested before cutting and serving them. The rest period allows for temperature gradients in the meat to even out, slowly cooling the exterior while the interior meat continues to rise in temperature. It also allows the muscle fibers to relax, reabsorbing the juices that they may have squeezed out in cooking.
We did some tests on this and found that during the rest period, our exterior temperature dropped while the interior temperatures continued to rise slightly. Perfect.
How to Carve Your Prime Rib Roast:
How you choose to carve your meat is up to you, but there are two—rather obvious—things that we want to point out. First, take off all the string you used to tie the roast up! No one wants to find a piece of cotton butcher twine caught in their teeth during a delicious dinner. Second, slice perpendicular to the cylinder. Don’t carve down the length of the roast…it will not be good!
Those two basics aside, thin slices or fat slabs are your prerogative. Use a sharp knife and go for it.
What About Reverse Searing?
One of the appealing features of a prime rib is the salty, seasoned, beefy outer layer. Many methods include an instruction to reverse sear (sear after cooking) your roast to increase the crispiness. We wanted to keep the flavor and food safety advantages of pre-searing but also wanted to see if a final sear could give us just one little bit of extra enjoyment. So, we cooked another rib roast. For this one, we set our ChefAlarm to 115°F (46.1°C) so that we would be able to move the meat to a hot oven with thermal room to spare. As the roast approached pull temp, we preheated a second oven to 500°F (260°C).
When the alarm sounded, we reset it to 120°F (49°C) and moved the roast to the hot oven. The roast started to sizzle and sing almost immediately. It became steadily more brown and crisp on the outside. When we reached the next alarm point (set lower to account for the increased oven heat that would drive more carryover cooking), we removed the roast, let it rest, cut into it, and were disappointed to find a very noticeable gray ring, up to 1″ thick. In the end, the thicker crust that we got from the final sear was not worth the vast swaths of rosy pink meat that were lost.
We recommend a low, slow cook preceded by a good sear. Whatever crust you may get from the final sear is just not worth the risk to the rest of this exquisite cut of meat. And with the freezer method, you can get a harder sear without worrying about a gray ring from the beginning.
How to Select the Best Prime Rib Roast:
Picking out a rib roast at the store is a big deal. You want the best roast you can get in your price range, but you don’t want to come up short at dinner. So what should you buy and how much of it should you get? Let’s look first at grading and quality.
It’s a little known fact, but the method of grading beef by the USDA is solely based on fat marbling. The more thoroughly marbled the beef, the higher the grade. Higher graded beef will be juicier, more tender, and more flavorful, but it will also cost significantly more.
Buy the highest grade you can on your budget. If you can afford Prime grade, go for it! But Choice is generally a good intersection of quality and affordability.
You may have heard that Prime Rib refers to a prime-grade rib roast. This is not true—at least, not necessarily. The term “prime rib” predates the USDA meat grading system and is a reference only to the fact that it is the best part of the rib section. In fact in the USDA Food Standards and Labeling Policy Book, (pg 146), the USDA clearly states that, “PRIME RIB OF BEEF OR STANDING BEEF RIB ROAST FOR PRIME RIB: These products do not have to be derived from USDA prime grade beef” (emphasis in original).
Prime rib can be graded USDA Prime (it will cost you!), but it can also be USDA Choice or USDA Select. “Ungraded” meat cuts are also available, but if it were my decision, I’d get a little less of the better stuff than more of the ungraded.
So how much of this delicious, pricey beef do you need? That really depends on you and your guests, but as a general rule, figure about 1/2 pound of raw roast per person on a boneless roast, or one bone per two people on a bone-in roast.
What Even Is Prime Rib?
A prime rib can go by other names—beef rib roast, ribeye roast, or standing rib roast (so called when it is bone-in and can be roasted without the meat touching the pan)—but regardless of what it is called, it comes from the 6th through 12th ribs of a steer, sandwiched between the chuck and the short loin. It is primarily composed of the longissimus dorsi muscle that runs next to the spine. Because of its location high up on the back of the steer, this muscle is not well used. This lack of use means that this muscle develops to be much more tender than, say, the rear-leg muscles (the Round of beef): it is anatomically predisposed to tenderness.
Tenderness is, of course, only one of the attractive characteristics of this cut of meat. Perhaps the most notable feature of this cut is the deep, rich fat marbling. The “eye” of the rib is encircled by a ring of fat and connective tissue, outside of which lies the “lip” of the roast. Much of the whole roast is covered by a fat cap of varying thickness. It is those seams of fat that deliver rich flavor and a velvety texture, as well as keep the meat from drying out easily.
And, just in case you prefer a different doneness temperature, here is a helpful prime rib doneness temperature chart as a downloadable image…
Perfect prime rib is all about temperature control. Here’s how to get it just right.
- 1 prime rib, size determined by need
- Kosher salt
- Freshly ground black pepper
- Trim your rib how you like it best.
- Generously salt the roast, insert a thermometer probe near the edge of the roast, set the low-temp alarm of your ChefAlarm for 30°F (-1°C) and place the roast in the freezer.
- Meanwhile, preheat your oven to 225°F (107°C).
- When the low-temp alarm sounds, remove your roast from the freezer.
- Heat a heavy skillet (cast iron is preferred here) over high heat.
- Sear the roast well on all sides in the skillet.
- Season with pepper and/or any other seasonings you like.
- Place the roast on a rack set into a rimmed baking sheet. Insert a probe into the very center and set the high-temp alarm for 125°F (52°C).
- Cook the roast in the oven until the high-temp alarm sounds. Verify that there are no lower temperatures in the meat with your Thermapen Mk4.
- Remove the meat from your oven and let it rest for 30 minutes, lightly tented with foil.
- Carve and serve!
Keywords: Prime Rib Roast, Christmas Roast
Harold McGee, On Food and Cooking
Meathead Goldwyn, AmazingRibs.com
U.S. Department of Agriculture, USDA Food Standards and Labeling Policy Book