Leftover Prime Rib Sandwich – a delightful and simple way to transform leftover prime rib into a flavorful, satisfying sandwich. Easy to assemble and bursting with balanced flavors, this is a go-to for using holiday leftovers or any time you have extra roast beef on hand.
The BEST Leftover Prime Rib Sandwich
Each year after a big roast—whether a traditional standing rib roast, smoked prime rib, or grilled prime rib—many of us have delicious slices of beef left in the refrigerator. Turning those slices into a prime rib sandwich is one of the best, quickest ways to enjoy that meat again. The sandwich highlights the rich flavor of the prime rib while keeping preparation minimal. A smear of butter on the bread, a little horseradish sauce for bite, and a helping of sweet caramelized onions bring everything together for a sandwich that feels indulgent without much fuss.
What You Will Need
- Bread – two slices of your favorite sandwich bread, roll, or rustic loaf. Choose a sturdy bread if you plan to dip the sandwich in au jus.
- Butter – softened butter spread on the bread adds flavor and helps create a crisp, golden exterior if you decide to toast the sandwich.
- Leftover prime rib – thinly sliced prime rib, from the roast you prepared earlier. Room-temperature slices are easiest to layer.
- Horseradish sauce – a sharp horseradish cream or prepared horseradish sauce complements the beef beautifully. Adjust the amount to taste.
- Caramelized onions – sweet, slowly cooked onions bring contrast to the savory meat and spicy sauce.
Best Options for Toppings
Caramelized onions and horseradish sauce are our favorite pairings, but you can customize the sandwich easily. Add a slice of melting cheese like provolone, Swiss, or sharp cheddar for a richer sandwich. A light spread of Dijon mustard adds a tangy edge. If you like a saucier bite, serve with a small bowl of warm au jus for dipping. Crisp lettuce or pickles provide a fresh textural contrast.
How Long Can You Keep Leftover Prime Rib in the Refrigerator?
Store leftover prime rib tightly wrapped in plastic wrap or in an airtight container in the refrigerator. For best quality, eat the meat within 5–7 days. If you want to keep it longer, freeze slices in a freezer-safe bag or container for up to 6 months. Thaw in the refrigerator before using.
How to Make a Leftover Prime Rib Sandwich
Making this sandwich takes only a few minutes. The steps below keep the sandwich quick while letting the flavors shine.
Step 1 – Prep the Bread: Spread softened butter on both slices of bread. If you like a toasted finish, heat a skillet and toast the buttered sides until golden.
Step 2 – Mix or Add the Horseradish Sauce: If using homemade horseradish sauce, mix to taste. Spread 2–3 tablespoons over one slice of the bread. Adjust the amount depending on how much heat you prefer.
Step 3 – Add the Prime Rib and Onions: Layer 3–4 slices of leftover prime rib across the horseradish-smeared slice. Top with about 1/4 cup caramelized onions per sandwich. The warmth of the meat will release aromatics and meld flavors quickly.
Step 4 – Finish and Serve: Place the other slice of buttered bread on top, buttered side down. If desired, press the sandwich lightly and cut in half. Serve immediately with optional au jus for dipping, a crisp side salad, or potato chips.
Ingredients (per sandwich)
- 2 pieces bread
- ½ tablespoon butter (or plant-based butter)
- 3–4 slices leftover prime rib
- 2–3 tablespoons horseradish sauce
- ¼ cup caramelized onions
Instructions
- Prep Bread: Spread butter on both slices of bread.
- Add Fillings: Place 3–4 slices of leftover prime rib on one slice. Add 2–3 tablespoons horseradish sauce and ¼ cup caramelized onions on top of the meat.
- Top & Serve: Close the sandwich with the second piece of bread, buttered side down. Cut in half and serve immediately.
Notes & Tips
- Type of Bread: Use any bread you enjoy—sourdough, ciabatta, baguette, or a soft roll all work well. For dipping, choose a sturdier bread.
- Reheating Leftovers: If your prime rib is chilled, let the slices come to room temperature for a few minutes or warm briefly in a skillet before assembling to enhance flavor.
- Variations: Add a slice of cheese and melt it quickly under a broiler or in a skillet for a richer sandwich. A smear of Dijon mustard or a few pickles can add brightness.
- Storage: Assemble sandwiches just before serving for best texture. Leftover components (meat, onions, sauce) keep separately in airtight containers for several days in the refrigerator.
Serving Suggestions
Serve the sandwich with a small bowl of warm au jus for dipping, a crisp green salad, roasted or pan-fried potatoes, or simple kettle chips for a comforting meal that comes together in minutes.
If you tried this recipe and enjoyed it, consider leaving a star rating and a short note about any substitutions or tweaks you made—the feedback helps refine and personalize the idea for other home cooks.