Cajun Prime Rib on the Grill

Sharing is caring!

Move over traditional prime rib – this Cajun prime rib brings BOLD flavor to your holiday table! Injected with Cajun butter and coated in spicy seasoning, this prime rib roast is packed with flavor from edge to edge, not just on the crust. After smoking hundreds of prime rib roasts, this is hands down the most flavorful one we’ve ever made!

If you’re tired of the same old prime rib routine year after year, it’s time to shake things up with some serious Cajun flair. This Cajun smoked prime rib recipe takes everything you love about a classic prime rib and cranks up the flavor dial to eleven.

My mother-in-law absolutely loves a Cajun or blackened style ribeye, and we don’t make it for her nearly enough. So this Cajun butter smoked prime rib is all for her – and let me tell you, it did NOT disappoint! If this doesn’t earn me son-in-law points, I don’t know what will.

*And be sure to check out our classic smoked prime rib recipe and our rotisserie prime rib!

What Makes this Cajun Prime Rib Different?

Let me be honest with you – most prime rib roasts, even really good ones, only have flavor on the outside where you’ve seasoned the crust. The inside is just pure beef flavor, which is why we typically serve it with creamy horseradish sauce or au jus for extra punch.

But THIS Cajun smoked prime rib? It’s completely different. By injecting the roast with a simple store-bought Cajun butter marinade AND seasoning the outside generously, you get flavor all the way through. Every single bite has that spicy, buttery, Cajun goodness.

This isn’t your grandmother’s prime rib – unless your grandmother is from Louisiana, in which case, she already knows what’s up.

Choosing Your Prime Rib Roast

For this recipe, I picked up a boneless prime rib roast from Costco at $10.99 per pound. Now, there are pros and cons to boneless versus bone-in roasts.

Boneless vs Bone-In

Bone-in advantages:

• Bones add extra flavor
• Bones protect the meat during cooking
• Makes for a more impressive presentation

Boneless advantages:

• Often less expensive per pound since you’re not paying for bone weight
• Easier to carve
• Still makes an incredible roast when properly prepared

At the end of the day, both work great for this recipe. Just remember – whether you go boneless or bone-in, you MUST truss it.

Why Trussing is Essential

This is very important: Even without bones, you need to truss your prime rib roast with butcher’s twine. Here’s why –

1. Prime rib has a fatty area that separates the spinalis (the outer cap) and the eye of the ribeye. Under heat, especially when injecting moisture like for this Cajun butter prime rib, the separation can cause the spinalis to lift apart.
2. Trussing the prime rib roast helps the meat to cook more evenly, and it prevents the gray ban from forming so that you have a beautiful roast that is pink all the way through.

I trussed my roast in three places to keep everything together, and it made all the difference in maintaining the roast’s shape during the cook.

Simply use butcher’s twine to tie the roast up tightly in three different cross sections, with the twine spaced out evenly. For a larger roast, you may need to tie it more than three times, about every 2″.

How Much Prime Rib Per Person

Plan on about 1 pound of bone-in prime rib per person, or about 3/4 pound per person for boneless. For this recipe, a 6-7 pound boneless roast will easily feed 8 people, especially if you serve it with the baby potatoes and onions, which I highly recommend.

Ingredients for Cajun Smoked Prime Rib

The beauty of this Cajun prime rib recipe is in its simplicity. You don’t need a ton of exotic ingredients to create something incredibly flavorful.

For the Roast:

• Prime rib roast – 6-7 pounds, boneless or bone-in
• Cajun butter injection – Store-bought works great! I used this Cajun butter injection that you can find at most grocery stores. Another popular choice is the Tony Chachere’s Creole Style Butter Injectable Marinade.
• Cajun seasoning – Use your favorite. Many Cajun or Creole seasonings are pretty salt-forward, so they act as a dry brine in this recipe. Plus, the Cajun seasoning gets added to butter for an easy Cajun butter coating.
• Butter – You’ll need one stick of butter. I recommend using unsalted butter since most Cajun seasonings are fairly salty.
• Butcher’s twine – For trussing

For the Potatoes and Onions (Optional but Recommended):

• Baby yellow potatoes
• Cipollini onions – Or you can use a large sweet onion cut into chunks

For the Blue Cheese Sauce (Optional):

• Roasted garlic – About 5-6 cloves
• Heavy cream – 1/2 cup
• Blue cheese crumbles

---

Grilling Notes

• Pellet Grill/Smoker Temp – About 250°F until the internal temp of the prime rib roast reaches about 117-118°F; then increase the grill temperature for searing
• Wood Used – Hickory
• Grill Used – Weber Summit Charcoal Grill (you can use any pellet grill, charcoal grill, or smoker)
• Smoking Time – About 3-4 hours total at 250°F, then an additional 10-15 minutes for the sear
• Internal Temperature – Pulled at 120°F, rose to about 125-126°F after resting (perfect medium-rare)

---

How to Make Cajun Prime Rib

The Day Before: Truss and Dry Brine

Step 1: Truss the roast. Before you do anything else, truss your prime rib roast in three places with butcher’s twine. This keeps the spinalis from separating during the cook.

Step 2: Apply Cajun seasoning generously. Remember, this is a LARGE piece of meat, and Cajun seasoning is typically very salt-heavy. This is intentional – it’s acting as a dry brine. Season all sides of the roast liberally with your Cajun seasoning, working it into every surface.

Step 3: Refrigerate overnight. Place your seasoned and trussed prime rib roast on a wire rack set on top of a sheet tray and refrigerate overnight. This allows the salt to penetrate the meat, adding extra flavor throughout and helping to tenderize the roast.

Day Of: Inject and Prep

Step 4: Inject with Cajun butter. Using a meat injector, inject the roast with Cajun butter in multiple spots. I used about 3/4 to 1 cup total of the injectable Cajun butter marinade for my 6.5 pound roast.

Step 5: Prepare your vegetables. If you’re making the potatoes and onions (highly recommended!), prep them now. Wash your baby yellow potatoes and peel your Cipolline onions. Or you could substitute one medium sweet onion cut into bite-sized chunks if you can’t find Cipolline onions.

Step 6: Set up your cooking vessel. Place your vegetables in the bottom of a roasting pan or baking sheet. Set a wire rack on top. This setup catches all those incredible Cajun butter drippings from the prime rib, which will flavor the potatoes and onions as the roast cooks. Trust me, don’t skip this step!

Making the Cajun Butter Rub

Step 7: Prepare the Cajun butter mixture. This step is simple but crucial. In a small bowl, mix one stick of softened butter with a generous amount of your favorite Cajun or Creole seasoning. Mix it well.

Step 8: Coat the roast with Cajun butter. Start with the bottom of the roast first, because you want to prepare the top of the prime rib last for a beautiful presentation. Slather that Cajun butter all over the roast, making sure to get butter evenly on all sides. The butter will drip down into those potatoes and onions during cooking – that’s pure flavor gold!

Smoking the Cajun Prime Rib

Step 9: Prep your grill or smoker. Preheat your pellet grill, charcoal grill, or smoker to 250°F. I cooked my Cajun prime rib on a charcoal grill and I added chunks of hickory wood for extra smoke flavor, but you could also use oak, pecan, or a fruit wood if you prefer a milder smoke flavor.

*For my Weber charcoal grill, I used the lazy man snake method with cut up hickory chunks added in. Start your coals on one end and let them burn through slowly for consistent heat.

Step 10: Smoke the prime rib. Place your roasting pan with the rack and prime rib on the grill. Close the lid and let it smoke at 250°F until the internal temperature reaches about 117-118°F. For my 6.5 pound roast, this took about 3.5 hours.

During this time, resist the urge to constantly check on it. Low and slow is the name of the game here.

The Final Sear (Reverse Sear Method)

Step 11: Remove the roast and crank up the heat. When your roast hits 117°F internal temperature, remove the entire sheet pan from the grill. *This is crucial – do NOT leave it on the grill while you’re raising the grill temperature, because then your roast won’t have as long to sear for the beautiful crust.

Increase your grill temperature to a higher heat for searing. While the grill is heating up, you can leave the potatoes on to continue to cook if needed. I found that my Cajun prime rib cooked more quickly than the potatoes. This is why it’s handy to have the prime rib set on a wire rack on top of the vegetables – you can easily remove the roast so that the potatoes can continue to cook by themselves.

Step 12: Sear the roast. Once your grill is hot, put the prime rib directly on the grill grates on the hottest part of the grill, and sear it on all sides. This should only take about 10-15 minutes total, or until the roast reaches your desired doneness. You’re looking for a beautiful, caramelized crust.

For a perfect medium rare, I removed my roast from the grill once it reached 120°F internal temperature. My Cajun prime rib roast went from 120°F to about 125-126°F during the 15-minute rest, which was exactly the medium-rare I was looking for.

Carving and Serving

Step 13: Remove the twine and carve. After the rest period, carefully remove the butcher’s twine. Use a sharp carving knife to cut the prime rib into steaks about 1/2″ to 1″ thick, depending on preference.

Serve the Cajun prime rib with those incredible Cajun butter potatoes and onions on the side. Drizzle the blue cheese sauce over the top or serve it on the side for dipping. Or serve your Cajun prime rib with this creamy horseradish sauce.

Making the Blue Cheese Sauce (Optional)

While the prime rib is resting, you can whip up this incredible blue cheese sauce, which we love for serving with blackened or Cajun-style beef:

In a small saucepan, combine about 1/2 cup of heavy cream with 5-6 cloves of mashed roasted garlic. Warm over medium heat, stirring occasionally. Once warmed through, add blue cheese crumbles and stir until melted and combined.

This is a super easy 3 ingredient sauce that’s absolutely phenomenal with the Cajun flavors. You can also add a little horseradish to make it a horseradish roasted garlic blue cheese sauce if you want!

Serving Suggestions

Those potatoes that cooked underneath the roast? They’re like cowboy butter potatoes with Cajun seasonings. They’re honestly so good, you could serve them as a standalone side dish.

For a complete meal, consider adding:

• The blue cheese sauce (recipe above)
• A simple green salad
• Roasted asparagus
• Horseradish sauce for those who want extra kick
• Dinner rolls to soak up all that Cajun butter
• Smoked twice baked potatoes

Important Note about the Cajun Injector Marinade

Full transparency here – when we made this recipe for the first time, we injected the roast with the Creole butter marinade the night before, and then we refrigerated it with the Cajun seasoning to dry brine overnight. However, we noticed some discoloration in the smoked prime rib when we cut into it. After talking with some folks, we think it might have been a chemical reaction from injecting the night before. The Cajun butter injection had citric acid in it, which may have “cooked” some of the meat similar to how ceviche works.

The good news? The prime rib was incredibly tender – probably the most tender prime rib we’ve ever made. So there might be a catch-22 with the acid breaking down the meat.

We recommend seasoning the roast and brining it overnight as instructed, but save the Cajun injection for the day of cooking, about 2-3 hours before it goes on the grill.

Pinterest User? Do us a favor and PIN this to your board for smoker or pellet grill recipes. This is a GREAT way to support us!

Sharing is caring!