Low and slow is the way to go when smoking a large prime rib roast. You won’t have to worry about burning the prime rib at 225 degrees and it’s not so low that the roast gets too dry. Let’s take a look at some things to consider and how long to cook prime rib at 225 degrees.
How Long to Cook Prime Rib at 225?
An average prime rib roast of 5 pounds will take 2.5 to 3.5 hours to cook to a tender, medium rare doneness. Plan on 35 to 40 minutes per pound for your prime rib. Using a remote temperature probe is a great way to keep an eye on the roast, but it’s not necessary if you only have a kitchen meat thermometer.
Bone-In vs. Boneless
The question of whether to purchase a bone-in or a boneless rib roast could be debated into the wee hours of the morning. We definitely prefer bone-in prime rib for the added flavor. Many pitmasters will actually cut off the ribs and use kitchen twine to tie them back onto the roast. This way the bones can be easily removed after cooking.
Smoking or grilling a prime rib with the rib bones will add more flavor that’s sure to impress. The rib bones will also protect the roast from overcooking on the bottom. Prime rib bones can be saved after cooking to add some heartiness to a soup or a special dog treat for that good boy!
Boneless rib roast doesn’t require as much preparation work as compared to bone-in prime rib. Your local supermarket may not always keep a bone-in prime rib in stock, leaving you with no choice but to cook a standing rib roast. Don’t worry, though. It will still be tender and delicious!
How to Prepare Prime Rib
Preparing your prime rib for the cook doesn’t take much effort, only patience. Prime rib should be set out at room temperature for 2 to 4 hours. This will allow the center of the roast to cook more evenly. You can skip this step if you’re too pressed for time, though we recommend including the pre-rest in your preparation.
While the prime rib is sitting out is the perfect time to trim any fat you’d like to remove. A thin layer of fat should be kept on the meat, but cut away any scraps of meat that may be left on the exposed part of the bones.
Once your rib roast is trimmed up, season it on all sides. Prime rib doesn’t need a large mix of spices and herbs since it will already be full of flavor on its own. Use your favorite seasoning blend or the classic salt, pepper and garlic. Kosher salt on its own would also do just fine.
Searing vs Reverse Searing
Searing prime rib is an important step that should never be overlooked. To sear your rib roast, set it on high heat of 450 to 500 degrees for 1 to 3 minutes on each side.
Reverse searing has become a popular method amongst BBQ enthusiasts. Reverse searing is simply searing the meat at the end of cooking instead of a regular sear before the meat has been cooked.
There are a few ways to sear the prime rib before you roast it. One great method is to sear it in a cast iron skillet on the stove, then transfer it to the smoker. If your smoker has a grate in the fire box, you can sear it there as you would a steak. You can also sear the rib roast in the cooking chamber of your smoker by increasing the heat for 5 to 10 minutes.
A gas or charcoal grill is much easier to use for searing your prime rib. Simply set the roast over high flames until all sides are crisp but not burnt. A reverse sear would be done the same way right before you pull the rib roast from the grill or smoker.
Grilling or Smoking Prime Rib Roast
Indirect heat is a must when it comes to cooking a prime rib roast. Either a grill or a smoker can get the job done. If you’re cooking on a grill, add wood chips to the fire to maximize a savory taste to the meat.
Mild flavored wood is best for prime rib so its own flavor doesn’t get overpowered by the smoke. Pecan, maple and oak are all good choices. Mesquite should be used sparingly to avoid a bitter aftertaste. Mesquite also burns very hot and can quickly cause an overheat.
Place the rib roast on the cool side of your grill away from direct heat. The cooking chamber will heat up like an oven and roast the prime rib to perfection.
If you’re cooking on a smoker, set the prime rib in the middle of the cooking chamber for best results. Smoking the rib roast will be easier to maintain a low 225 degrees throughout the cook due to the offset heat source. A wifi or bluetooth temperature probe inserted in the roast will make smoking a breeze and, as such, will give you an opportunity to sit back and enjoy your company!
When Prime Rib is Done
Monitor the temperature of the meat so you can be ready to pull it from the grill at just the right time.
We recommend cooking your prime rib to medium rare for a juicy and tender finish. Remember that the internal temperature of the prime rib will continue to increase while it’s resting. So, remove the roast when it reaches a target internal temperature of 124 to 129 degrees for a final medium rare temperature of about 135 degrees.
If rare prime rib is your preference, the roast should be cooked to an internal temperature of 118 to 122 degrees before you rest it. The final internal temperature of the roast should be 125 degrees for rare. Au jus sauce made from the meat drippings is an excellent garnish with rare prime rib.
Time for the Rest
Remove the prime rib from the grill or smoker when it reaches the target internal temperature and transfer it to a warm serving dish to rest. You can place a foil tent over the rib roast while it’s resting, but this may soften the bark a bit. Give the roast 15 minutes to rest if cooked to rare, or 30 minutes for medium rare.
Carving or Slicing a Prime Rib
Remove the rib bones before carving your prime rib by cutting the kitchen twine that secures them to the roast or cutting them off with a sharp slicing knife. Prime rib should be sliced fairly thin, around ¼-inch in thickness. The outside slices are best for those that might like their prime rib more done and the center cuts will be more tender and pink.
Final Thoughts
Slow smoking prime rib at 225 degrees is a great way to produce perfectly tender and moist roast. Rest your prime rib for 15 to 30 minutes after smoking or grilling it for 2-½ to 3-½ hours to lock in the juices and maximize tenderness. It’s a long process, but the results are definitely worth it!
