Treat yourself to the best Prime Rib Sandwich! You'll love how easy it is to prepare and how incredibly flavorful it is. It's the best way to use up these slow cooker prime rib leftovers. You only need a handful of staple ingredients that you probably already have on hand during the holiday season!
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Whether you're savoring the last bites of a holiday feast or elevating your everyday meals, this leftover prime rib sandwich recipe is a great way to enjoy those extra slices of the star of the show.
There's something truly satisfying about transforming leftover prime rib into a mouthwatering sandwich that hits all the right notes.
This prime rib sandwich recipe combines the rich flavors of succulent meat with sweet caramelized onions, homemade creamy horseradish sauce, peppery arugula, and melty cheese, all nestled between slices of a fresh baguette. It's a classic pairing.
If you are in the mood for something delicious and hand-held, you'll also love our spicy Italian grinder sandwich, our Philly cheesesteak sliders, or even this breakfast burger!
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❤️Why we love this recipe
- Perfect to use up leftovers. If you have lots of leftovers from Christmas dinner, this crave-worthy sandwich will stretch them even further. For us, it's almost our favorite part about preparing prime rib!
- Made with simple ingredients. This sandwich is made with basic ingredients, to create complex flavors. Anything you need for this recipe can be found at any grocery store.
- Easy to make. This recipe is perfect for both beginner cooks and seasoned chefs with our step-by-step instructions. It's an easy sandwich.
- Ultimate comfort food. Indulge in the decadence of prime rib with each bite. The sweet caramelized onions complement the savory prime rib, while the creamy horseradish sauce and peppery arugula add a zesty kick. The melted provolone cheese adds a sharp flavor that takes this sandwich to the next level.
🥖Ingredients
Here are the ingredients we used for this recipe. You can find more information for substitutions below.
- Leftover prime rib. Just make sure to slice it very thin, and remove any excess fat. For this sandwich, we don't want the extra fat, it just makes for a bit of a strange mouthfeel. We used leftovers from our slow cooker prime rib!
- Bread. Choose a crusty, hearty bread that will hold up well to a lot of toppings. We love getting a take-and-bake loaf at the store and having a nice hot, fresh baked baguette for our sandwiches!
- Creamy horseradish sauce. You can make this up to 6-7 days in advance and store it in the fridge in an airtight container.
Visit the recipe card for the full quantities and nutritional information.
✨Substitutions & Variations
Here are a few suggestions on additional flavors to try, or simple variations to this recipe.
- No white balsamic vinegar? Just use regular balsamic, or any vinegar you have on hand. The vinegar helps balance out the rich flavors in the caramelized onions.
- Experiment with different bread types, like ciabatta bread, a hoagie roll, french bread, or even a toasted bun, for a unique twist.
- Swap provolone for Swiss cheese, aged white cheddar, or your favorite cheese to tailor the flavor to your liking. We do recommend using something a little bit sharper in flavor here - as the caramelized onions and roast beef are really rich, so a sharp cheese balances out the flavors.
- Make it into a French dip. Serve with a side of au jus for dipping, transforming it into a French dip-inspired sandwich.
- Add a spicy kick. Add a bit of spicy mayo to the sandwich for a bit of spice!
- Add some Dijon mustard. There is a bit of Dijon in the horseradish sauce, but if you want an extra kick of mustard, it would complement this sandwich beautifully.
🔪Prep work
- If making your creamy horseradish sauce the day of, do this first and let it sit in the fridge while you work on the other ingredients.
- Prep the roast beef by slicing it very thin, and removing any excess fat.
- Use a sharp knife to thinly slice the onions.
- Preheat a large skillet over medium heat.
- If reheating the prime rib in the oven, preheat the oven to 300°F.
- Measure out all the remaining ingredients.
📋Instructions
Start with the caramelized onions. Melt the butter in a large skillet over medium-low heat. Add the sliced onions with a pinch of salt. (Image 1)
Cook, stirring occasionally, until they begin to soften and turn golden brown. (Images 2 & 3)
The process will take about 30 to 40 minutes to get to a deep golden brown color. (Image 4) Don’t rush this step; patience is key to creating perfectly caramelized onions.
Once the onions are a nice golden brown, stir in the balsamic vinegar and black pepper, and season to taste with salt. Cook for an additional 2–3 minutes, then remove from heat and set aside.
Meanwhile, while the onions are caramelizing, prepare the prime rib. If the prime rib is cold, gently reheat it in a pan over low heat, or wrap it in foil and warm it in a preheated oven at 300°F for about 10 minutes.
✨Pro Tip: If you have a meat slicer, now is the time to use it to make perfect thin slices of prime rib!
Slice the baguette lengthwise, and then cut it into the desired number of sandwiches. We made three large sandwiches. Place the baguette slices on a baking sheet.
Spread creamy horseradish sauce on both halves of the baguette. (Image 5)
Lay the thinly sliced prime rib over the sauce. Season with a bit of salt and pepper, if desired. (Image 6)
Top the meat with caramelized onions. (Image 7)
Add slices of provolone cheese on top of the onions. (Image 8)
Place the sandwich (open-faced) under the broiler for 2-3 minutes or until the cheese is melted and bubbly. Watch carefully to avoid burning. (Image 9)
Remove the sandwich from the oven and top with baby arugula, and season the arugula with kosher salt and pepper to taste. Add more horseradish sauce if desired. (Image 10)
Now, just assemble the sandwich, and enjoy!
✨Tips & tricks
- Take your time when caramelizing the onions. There’s no rushing it! Be patient when caramelizing onions; they add a rich, sweet flavor to the sandwich.
- Slice the prime rib very thin. Use a very sharp knife to get thin, even slices of prime rib.
- Remove the excess fat. Pull or cut off any pieces of extra fat on the prime rib. It won’t taste great to bite into a large chunk of fat on a sandwich!
- Carefully reheat the prime rib. You don’t want to overcook the meat, so heat it very gently. Also, keep in mind that it will heat up a little bit more under the broiler.
- Add horseradish sauce to taste. Adjust the amount of horseradish sauce to suit your preferences.
- Season the arugula. This will ensure that every bite tastes great.
- Watch the sandwich under the broiler closely to avoid burning while achieving that perfect, melty cheese texture.
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💭Frequently Asked Questions
Store leftover sandwiches in an airtight container in the fridge for up to two days.
To warm up prime rib for sandwiches, you've got a few options. First off, we don't recommend heating the arugula on the sandwich, so keep this off the sandwich if you can.
Use a non-stick pan on the stove with a bit of olive oil, turning the slices until they're warmed up.
Another way is to wrap the slices in foil and stick them in a 300°F oven for 10 minutes, or air fryer for about 5 minutes.
If you're in a hurry, the microwave works too. Set the microwave to 50% power, and just be sure to heat the slices in short bursts to avoid overdoing it.
No, we don't recommend freezing the entire sandwich. You can however freeze the prime rib slices for up to 3 months in a freezer safe and airtight container.
More Recipes To Consider
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📖 Recipe
Prime Rib Sandwich
Ingredients
- 4 tablespoons unsalted butter
- 1 tablespoon white balsamic vinegar
- ½ - 1 teaspoon kosher salt, divided
- ¼ - ½ teaspoon black pepper, divided (to taste)
- 1 pound leftover prime rib, thinly sliced and fat removed
- 1 large baguette, sliced in half lengthwise and cut into about 4 sections
- 4 - 6 slices provolone cheese
- 2 ounces baby arugula (to taste)
- 6 tablespoons creamy horseradish sauce (about 3 servings)
Instructions
- Start with the caramelized onions. Melt the butter in a large skillet over medium-low heat. Add the sliced onions with a pinch of salt. Cook, stirring occasionally, until they begin to soften and turn golden brown. The process will take about 30 to 40 minutes to get to a deep golden brown color. Don’t rush this step; patience is key to creating perfectly caramelized onions.
- Once the onions are a nice golden brown, stir in the balsamic vinegar and black pepper, and season to taste with salt. Cook for an additional 2–3 minutes, then remove from heat and set aside.
- Meanwhile, while the onions are caramelizing, prepare the prime rib. If the prime rib is cold, gently reheat it in a pan over low heat, or wrap it in foil and warm it in a preheated oven at 300°F for about 10 minutes.
- Slice the baguette lengthwise, and then cut it into the desired number of sandwiches. We made three large sandwiches (or 6 small - medium sized ones). Place the baguette slices on a baking sheet.
- Spread creamy horseradish sauce on both halves of the baguette. Lay the thinly sliced prime rib over the sauce. Season with a bit of salt and pepper, if desired. Top the meat with caramelized onions.
- Add slices of provolone cheese on top of the onions. (About 1.5 slices per sandwich). Place the sandwich (open-faced) under the broiler for 2-3 minutes or until the cheese is melted and bubbly. Watch carefully to avoid burning.
- Remove the sandwich from the oven and top with baby arugula, and season the arugula with kosher salt and pepper to taste. Add more horseradish sauce if desired. Now, just assemble the sandwich, and enjoy!
- Store leftover sandwiches in an airtight container in the fridge for up to two days.
Save This Recipe! 💌
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Notes
- Take your time when caramelizing the onions. There’s no rushing it! Be patient when caramelizing onions; they add a rich, sweet flavor to the sandwich.
- Slice the prime rib very thin. Use a very sharp knife to get thin, even slices of prime rib. Remove the excess fat. Pull or cut off any pieces of extra fat on the prime rib. It won’t taste great to bite into a large chunk of fat on a sandwich!
- Carefully reheat the prime rib. You don’t want to overcook the meat, so heat it very gently. Also, keep in mind that it will heat up a little bit more under the broiler.
- Add horseradish sauce to taste. Adjust the amount of horseradish sauce to suit your preferences.
- Season the arugula. This will ensure that every bite tastes great.
- Watch the sandwich under the broiler closely to avoid burning while achieving that perfect, melty cheese texture.
- To reheat. To warm up prime rib for sandwiches, you've got a few options. First off, we don't recommend heating the arugula on the sandwich, so keep this off the sandwich if you can.
- Use a non-stick pan on the stove with a bit of olive oil, turning the slices until they're warmed up.
- Use the oven or air fryer. Another way is to wrap the slices in foil and stick them in a 300°F oven for 10 minutes, or air fryer for about 5 minutes.
- If you're in a hurry, you can even use the microwave. Set the microwave to 50% power, and just be sure to heat the slices in short bursts to avoid overdoing it.
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