There are sandwiches, and then there are roast beef sandwiches that stop time. This one is in the second category. It’s the kind of sandwich that made my father pause mid-bite and say, “You made this?”—his voice somewhere between awe and disbelief. It’s the kind of meal that disappears faster than you can pour the drinks. And honestly, I didn’t realize how addictive it was until I made it for a lazy Sunday lunch and found myself making it again the next day… and the day after that.
With layers of tender roast beef (warm or cold!), sharp cheddar melting slightly into the toasted bread, caramelized onions, peppery arugula, a smear of horseradish mayo, and the subtle tang of Dijon—it’s the kind of sandwich that feels like a feast but eats like a quick lunch. The flavors are bold, complex, yet so comforting. You can serve it with soup, salad, fries, or just eat two and call it a meal!
Let’s dive into the heart of this glorious sandwich so you can start your own little tradition around it, too.
Preparation Time
Preparation: 15 minutes
Cooking (if caramelizing onions or heating beef): 20 minutes
Assembly: 5 minutes
Total time: ~35–40 minutes
Serves: 2 very hungry people or 3–4 with sides
Difficulty: Easy to Medium (depending on how far you take the toppings)
Now let’s talk ingredients—because this sandwich is wildly customizable, and I’ll show you every way.
The Necessary Ingredients (Possible in All Kinds of Variations)
6–8 slices of quality roast beef (deli-style or homemade)
2 hoagie rolls, ciabatta, sourdough slices, or baguette (your call!)
4 slices of sharp cheddar cheese (or provolone, Swiss, or blue cheese for funk)
1 cup caramelized onions (takes ~20 mins but worth every second)
1 cup fresh arugula or baby spinach
2 tablespoons mayonnaise
1 tablespoon prepared horseradish (more or less to taste)
1 teaspoon Dijon mustard
Butter for toasting the bread
Optional: sliced pickles, tomatoes, roasted red peppers, banana peppers
Ingredient Alternatives:
Vegan: Use plant-based roast beef or seasoned portobello mushroom slices, vegan cheese, and vegan mayo + horseradish.
Gluten-free: Use certified gluten-free bread or rolls.
Dairy-free: Use dairy-free cheese or skip the cheese entirely—the sandwich still shines.
Low-carb: Swap bread for large lettuce leaves or a low-carb wrap.
Now let’s build this flavor bomb step-by-step, just like I’ve done countless times when feeding friends or building myself a midnight masterpiece.
The Steps of Preparation (Possible in All Kinds of Variations)
There are many ways to prepare this sandwich: warm or cold, grilled or not. Here’s how I usually do it when I want that melty-cheesy, cozy feel. Cold version? Just skip the heating and enjoy as-is.
Thinly slice your onions and caramelize them slowly in a pan with olive oil and a pinch of salt over low-medium heat for 20–25 minutes until golden and sweet.
While onions cook, mix the mayonnaise, horseradish, and Dijon mustard together in a small bowl. Adjust for heat and taste.
Lightly butter the insides of your bread and toast them cut-side down in a hot skillet or grill pan until golden.
Spread the horseradish mayo mixture generously on both sides of the toasted bread.
Lay down slices of cheddar cheese first (so it melts slightly from the warmth of the beef).
Layer on your roast beef—if you prefer it hot, warm the slices in a pan for 1–2 minutes before placing on the sandwich.
Top with the caramelized onions.
Add fresh arugula or greens of choice.
Add any extra toppings now—pickles, tomatoes, peppers, whatever makes you happy.
Close the sandwich, press gently, slice in half, and serve hot or cold!
Whether you’re making this on the fly or prepping ahead for a picnic or work lunch, it holds together beautifully and travels well.
Nutritional Benefits of This Recipe
Rich in Protein: Roast beef offers a generous dose of high-quality protein to fuel your body and keep you full longer.
Iron-Boosting: Red meat like beef is high in iron, which is essential for energy and focus.
Calcium and Vitamin D (from cheese): Supports strong bones and muscles.
Healthy Fats (from olive oil & mayo): Helps absorb nutrients and keeps you satiated.
Antioxidants (from arugula and onions): Great for inflammation and immunity.
Low Sugar: Naturally low in added sugars (unless you use sweetened bread or sauces).
Balanced Meal: Offers carbs, fat, protein, and greens in one compact, delicious form.
Possible Additions or Upgrades to This Recipe
Add a fried or poached egg on top for a brunchy twist.
Use truffle mayo instead of horseradish for a fancy version.
Swap in garlic aioli for a Mediterranean flavor.
Add a slice of crispy bacon for extra crunch and richness.
Serve with a side of au jus or beef broth for dipping—like a French Dip!
Top with crispy fried onions instead of caramelized for crunch.
Use fresh herbs like thyme or rosemary in the mayo for an aromatic kick.
Grill the entire sandwich panini-style for crispy edges.
Now that we’ve built it, let’s answer some of the most common questions I get about this masterpiece of a sandwich.
Frequently Asked Questions
Can I use leftover roast beef instead of deli slices?
Yes, and it’s actually even better! Thinly slice it and reheat gently in a pan with a little broth or butter.
What’s the best bread for this sandwich?
Ciabatta or hoagie rolls are my go-to for the right balance of chew and crisp, but sourdough or baguette work beautifully too.
Can I make this ahead of time?
Absolutely—just assemble everything except the arugula and toast, wrap in foil, and toast/reheat when ready.
Is horseradish spicy?
It’s got a nasal kick but isn’t hot like chili. You can add more mayo to tone it down or omit it if sensitive.
What cheese goes best with roast beef?
Sharp cheddar, provolone, Swiss, or blue cheese all work well depending on how bold you want to go.
Can I make it cold?
Yes! Skip the heating and make it like a deli-style sandwich. Still amazing.
What sauces can I substitute if I don’t like mayo?
Greek yogurt with horseradish, mustard alone, or even hummus for a twist.
Can I serve this at a party?
Yes! Make mini versions on slider buns or as pinwheels with wraps.
Is this sandwich freezer-friendly?
I wouldn’t recommend freezing it fully made, but you can freeze the caramelized onions and cooked beef for later use.
Can I turn this into a wrap or salad?
Totally. Use a wrap instead of bread or toss all ingredients into a salad bowl with your favorite vinaigrette.
From my kitchen to yours, I truly hope this roast beef sandwich becomes a staple in your rotation. It has carried me through lazy weekends, surprise guests, late-night cravings, and even a few impromptu backyard picnics. There’s just something about that combo of beef, cheese, and tangy kick that never gets old.
Please share this recipe with your friends, post your sandwiches on social media, and tag me—I’d LOVE to see your creations!
