Grilled Steak Sandwich with Chimichurri

One bite of this grilled steak sandwich with chimichurri—loaded with juicy steak, melted cheese, and golden onions on toasty bread—and you’ll instantly regret sharing. It’s a hearty, gloriously messy masterpiece that delivers big flavors and earns you serious “grill master” bragging rights with every serving.

Two grilled steak sandwiches on rustic bread, packed with juicy slices of steak, melted cheese, and vibrant green chimichurri sauce, shown close up for a hearty, craveable meal.

Why You’ll Love This Grilled Steak Sandwich with Chimichurri

All the flavors: Savory steak, bright chimichurri, creamy cheese, crispy onions… every bite is a flavor bomb.
Big sandwich energy: Feeds a crowd, or just yourself with zero regrets.
Customizable: Mix up the cheese, bread, or toppings. No rules—just joy.
Serious comfort food: For days when you want to treat yourself (or just need to win “best dinner ever”).

Ingredients & Swaps

What You’ll Need

Steak: 2–3 filet mignon (for ultimate tenderness), but strip, sirloin, or even leftover grilled steak work great.
Steak rub/seasoning: Use your favorite, or just salt, pepper, and garlic powder.
Oil: For grilling steak and frying onions. Canola, avocado, or any neutral oil.
White onion: Thinly sliced for frying.
Ciabatta bread: Or any sturdy bread that crisps up well—think baguette or sourdough.
Provolone cheese: Melty and mild, but Swiss, mozzarella, or even sharp cheddar are all winners.
Horseradish aioli: Mayo mixed with a little horseradish and garlic. (Totally optional but highly recommended!)
Chimichurri: Homemade (parsley, garlic, olive oil, red wine vinegar, chili flakes, salt & pepper) or your favorite jarred version.

For precise amounts, check the recipe card at the end of the post.

All the ingredients for steak sandwiches on a marble countertop: filet steaks, ciabatta, onions, provolone cheese, horseradish aioli, and chimichurri.

Ingredient Swaps

No filet? Flank, skirt, or ribeye bring lots of flavor (just slice thin!).
Gluten-free? Use your favorite GF bread.
No horseradish? Go classic garlic aioli or even spicy mayo.

How to Make the Ultimate Grilled Steak Sandwich with Chimichurri

This recipe brings together juicy grilled steak, crispy onions, toasty bread, and a swoon-worthy green sauce in just a few simple steps. Trust me, the hardest part is waiting to dig in.

Instructions

Prep the Onions: Thinly slice your white onion, then pat dry with paper towels to avoid oil splatters.
Fry the Onions: Heat 1 inch of oil in a skillet to 350°F. Fry onions in batches for 2–3 minutes until golden and crisp. Drain on paper towels and season with salt, pepper, and garlic powder. Keep warm.

Thinly sliced onions bubbling and crisping in a skillet of hot oil, ready for steak sandwich toppings.

A pile of golden, crispy fried onions held up on a spoon above a skillet, perfect for topping steak sandwiches.

Make the Chimichurri: In a bowl, mix ½ cup chopped parsley, 3 minced garlic cloves, ¾ cup olive oil, ¼ cup red wine vinegar, 1 teaspoon red pepper flakes, and a pinch each of salt and pepper. Stir and set aside (can be made ahead!).

A spoonful of homemade chimichurri sauce with chopped herbs, red chili, and olive oil held over a wooden bowl.

Season & Grill the Steak: Rub steaks with oil and your favorite seasoning. Grill over medium-high (about 375°F) for 3–4 minutes per side (or until 120°F inside for medium-rare). Rest for 10 minutes, then slice thinly.

Two thick filet steaks coated in steak rub, sizzling on a hot grill over glowing coals.

Two filet steaks with dark grill marks, perfectly cooked over open flames on a grill.

Juicy grilled steak sliced into strips on a wooden cutting board, showing a pink, tender center and a crispy, charred crust.

Toast the Bread: Slice ciabatta in half and toast on the grill until golden.
Assemble: Slather bottom bread with aioli. Layer on sliced steak, fried onions, provolone cheese, and a generous drizzle of chimichurri. Top with more aioli and the other half of bread.

Sliced grilled steak piled high on toasted bread and topped with crispy fried onions, served on a white plate.

Open-faced sandwich with sliced grilled steak, melted provolone cheese, and a generous spoonful of chimichurri sauce on toasted bread.

A grilled steak sandwich on a ciabatta roll, layered with juicy sliced steak, melted provolone cheese, crispy fried onions, and a generous spoonful of fresh chimichurri sauce.

Serve: Cut in half, grab extra napkins, and enjoy every glorious bite!

Sliced ciabatta sandwich filled with grilled steak, creamy cheese, and fresh chimichurri sauce.

Chloe’s Cozy Sandwich Tips

Don’t skip the rest: Giving steak time to rest keeps it juicy.
Slice thin: Slicing steak thinly makes for the perfect bite every time.
Fry onions last-minute: So they stay crisp and hot when you pile them on.
Go big with the sauce: Don’t be shy with that chimichurri—it’s what makes the sandwich sing.
Meal prep magic: Chimichurri and aioli keep in the fridge, so you can have sandwich greatness on demand.

Serving Ideas & Storage Tips

Crowd-pleaser: Slice into mini sandwiches for game day or parties.
Leftovers: Store steak, onions, and sauces separately in airtight containers. Assemble just before eating for best texture.
Quick lunch: Reheat steak gently, then build your sandwich fresh.

The Story Behind the Sandwich

If you know me, you know sandwiches are a love language around here. This grilled steak sandwich with chimichurri started as a backyard “what if…” experiment and quickly became a family obsession. The combo of juicy steak, crispy onions, melty cheese, and that zesty green sauce checks all my comfort food boxes. Whether you’re serving it for game night or just want to treat yourself, it’s impossible not to smile (and maybe get a little messy) with this in your hands.

A side view of a steak sandwich on a plate, stacked with grilled steak, provolone cheese, fried onions, and chimichurri.

FAQ

Can I use another cut of steak?

Yes! Flank, skirt, sirloin, or ribeye work well—just grill to your liking and slice thinly.

What’s the best bread for steak sandwiches?

Ciabatta is perfect for its crisp exterior and chewy inside, but sourdough, French bread, or a sturdy roll also work great.

Do I have to fry the onions?

Nope, but you’ll miss the crunch! You can use caramelized onions or even raw if you’re pressed for time.

Can I make this ahead?

Absolutely. Prep chimichurri and aioli up to 3 days ahead. Grill steak and fry onions just before serving for max freshness.