Prime Rib Steak Sandwiches

4.35 from 26 votes
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What do you do with leftover prime rib? Make an out-of-this-world Prime Rib Steak Sandwich, filled with tender meat, melted cheese, and sweet caramelized onions, that’s what.

This is pretty much the greatest sandwich there ever was!

Smoked Prime Rib Steak Sandwiches. on a plate.
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It’s possible you’re here because you saw our recipe for Smoked Prime Rib. If not feel free to check it out. It also comes with a video.

Or you may be here because you cooked a prime rib over the holidays and now find yourself with an influx of leftover prime rib. #meatloverproblems

Perfect Smoked Prime Rib on a cutting board

Or you’re just having mad cravings for an overindulgent meaty, cheesy, creamy, prime rib steak sandwich layered with the sweet goodness of caramelized onions.

Whatever the reason, we have the answer. It lies within the sweet, smoky, meaty, goodness of this sandwich.

Sandwiches using leftover holiday beef roast

This is the BEST use for leftover Prime Rib (smoked or otherwise).

Or any leftover steak really. And it’s as simple as warming up your meat, cooking some onions, and assembling.

How Do You Warm Up a Precooked Prime Rib?

Depending on how much steak you have, there are several options for warming up your meat. If you have about 2 lbs, like you see in the photo then you can take your roast and place it in the oven, set to 325, for about 15 minutes or until warmed throughout. You can use an instant read thermometer to avoid overcooking the meat. You don’t want to start cooking it again, you just want to warm it up. The length of time it will require to re-heat will depend on how much meat you have.

Reheating Prime Rib in the Oven

You can also just slice the cold meat and heat it up on the stove-top. You can also serve the meat cold. I won’t judge. But really, this prime rib steak sandwich is best made warm, with the ooey goodness of melted cheese smothering the warmed meat.

How to Caramelize Onions

While the meat is warming you can caramelize your onions. Just slice one onion and cook it on the stove-top until slowly caramelized and sweet. This takes time for perfect caramelization. Roughly 30-40 minutes if you’re doing it right. But believe me, it’s worth every single minute for the sweet glory of perfectly caramelized onions.

While all this is going on you can prep your creamy horseradish sauce. If you’re a traditionalist then it’s possible you used horseradish when you made your prime rib? Therefore it’s possible you have some leftover? If so you can just use that to make this creamy sauce. Or if you frequently make Bloody Mary’s at home then it’s likely you already have some in your fridge. And for all you mayo-haters out there (I’m raising my hand high), this sauce is mayo-free. I want something creamy, but not too rich or oily. So I like sour cream as the base, then add in horseradish, chives and a few other ingredients for flavor.

Next all we need to do is assemble the steak sandwich.

The Best Prime Rib Steak Sandwiches

How to Make the Best Leftover Prime Rib Steak Sandwich

To start I like a baguette for ease and crunch and for serving a group. And if you’re serving 4 or 5 people, it’s the perfect size.

  1. Portion the baguette into about 5-inch segments, and slice open lengthwise.
  2. Place a couple slices of provolone cheese on the bottom piece and place the bread and cheese under the broiler to melt.
  3. Once the cheese is melted (around 2 minutes), you can layer on your meat, arugula (or other crunchy greens), caramelized onions, and top with a generous drizzle of the horseradish cream sauce.

And you’ve got a winning leftover prime rib sandwich. Who knows, you may start smoking a prime rib just so you can use the tender slices to make these sandwiches? Just sayin.

Smoked Prime Rib Steak Sandwiches on parchment paper with a glass of beer

Prime Rib Recipes

Prime Rib Sandwich Recipe

Smoked Prime Rib Steak Sandwiches. And incredible use for leftover prime rib
4.35 from 26 votes

Prime Rib Steak Sandwiches

An incredible use for leftover prime rib? Prime rib steak sandwiches layered with melted provolone cheese, slices of prime rib, caramelized onions, arugula, and horseradish cream sauce.
Prep: 45 minutes
Cook: 40 minutes
Total: 1 hour 25 minutes
Servings: 4 sandwiches
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  • 1 ½ lbs leftover prime rib, or other steak (about 4-6 oz per person)
  • 1 white onion, sliced
  • 8 slices provolone cheese
  • 2 cups arugula, or other crunchy green, lightly packed
  • 1 large baguette

For the Horseradish Cream Sauce

  • ¾ cup sour cream
  • 3 tablespoons horseradish
  • 1 tablespoon Dijon mustard
  • 2 tablespoons fresh squeezed lemon juice
  • 1 tablespoon white wine vinegar
  • ½ teaspoon kosher salt
  • 2 tablespoon fresh chives, finely chopped


For the Prime Rib Sandwiches:

  • Preheat oven to 325 degrees.
  • To make the caramelized onions: heat up a large pan on the stovetop to medium heat then add 2 tablespoons olive oil and the sliced onions. Stir occasionally until the onions are soft, golden/starting to brown, and sweet to the taste (roughly 30-40 minutes). Remove from heat. *You may need to adjust the heat and turn it down if they are browning too fast.
  • In the meantime, place your leftover prime rib in a large cast iron (or oven proof) pan and place in the oven to heat up (approx 15 – 20 minutes). Remove from oven and slice into thin slices.
  • To build your sandwiches: cut the baguette into 4 equal size pieces and cut in half, lengthwise. Place on a baking sheet, open faced, and place two pieces of cheese on bottom half of each sandwich.
  • Place under the broiler for a couple minutes to melt the cheese (paying close attention to not burn the bread).
  • Once the cheese is melted, remove from the oven and build each sandwich: add 3-4 slices of the warm steak, a small handful of arugula, and a couple tablespoons of caramelized onions, then top with 1-2 tablespoons of creamy horseradish sauce. Serve immediately and enjoy the heck out of these epic sandwiches.

For the Horseradish Cream Sauce

  • Place all ingredients in a bowl and mix together.


If your steak is already sliced up you can just warm it up on the stovetop on on a small skillet. Alternatively you can add the thin steak slices on top of the provolone just before placing into the oven to broil and melt the cheese.


Calories: 768kcal | Carbohydrates: 11g | Protein: 35g | Fat: 64g | Saturated Fat: 30g | Cholesterol: 152mg | Sodium: 874mg | Potassium: 594mg | Fiber: 1g | Sugar: 4g | Vitamin A: 906IU | Vitamin C: 11mg | Calcium: 382mg | Iron: 3mg

Nutrition information is automatically calculated, so should only be used as an approximation.

Additional Info

Prep Time: 45 minutes
Cook Time: 40 minutes
Total Time: 1 hour 25 minutes
Course: easy
Cuisine: barbecue, bbq, lunch, prime rib roast, sandwich
Servings: 4 sandwiches
Calories: 768
Keyword: leftover steak recipe, prime rib sandwich, steak sandwich recipes, steak sandwich sauce
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About Mary

I'm Mary, a wine/food/travel writer, Certified Sommelier, mom of twins, former vegetarian turned BBQ fanatic, runner, founder of Vindulge, and author of Fire + Wine cookbook. Thanks for stopping by!

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4.35 from 26 votes (16 ratings without comment)

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  1. 5 stars
    This was the perfect recipe for our leftover ribeye roast. It was delicious and hit the spot. All of my children finished their sandwich and asked for seconds. The horseradish sauce was beyond and just scrumdiddlyumptious.