Grilled Steak & Onion Sandwiches
1 year ago

Grilled Steak & Onion Sandwiches with Creamy Horseradish Sauce

A great way to use leftover steak! Twin Cities food blogger greens & chocolate shares her go-to steak sandwich recipe.

While we are more burgers-and-brats type of people when it comes to grilling (and give me ALL the sides!), we do like to grill steaks a few times a summer. Paired with some grilled onions and mushrooms, an ear or two of corn on the cob and an ice cold beer … and I am one happy lady.

Since I tend to overdo it on the sides, I pretty much always have leftover steak. I’m definitely not one to waste a good piece of meat, but leftover steak on its own just doesn’t have quite the same appeal as the juicy, pink-in-the-middle steak that comes straight off the grill.

Enter the steak sandwich. Leftover steak is ideal for a steak sandwich because the key to a good steak sandwich is getting super thin slices of steak. When you cut the steak cold, it’s a lot easier to get thinner slices than when it’s hot. Another pro tip: cut the steak against the grain.

That said, these Grilled Steak & Onion Sandwiches with Creamy Horseradish Sauce were still 100% delicious with freshly grilled steak. The slices were just cut a little thicker than ideal. I’ve included directions on grilling the steak and onions, which is all very straightforward, but feel free to use any leftover steak you might have.

The star in these sandwiches is definitely the creamy horseradish sauce. I used to be one of those people who “didn’t like horseradish” but really didn’t know what they were talking about. I also used to dip my steak in ketchup. Please forgive me. I’ve come a long way since those days.

Anyway, this creamy horseradish dip is pretty much your steak’s new best friend. It’s SO good and SO easy. The base of the sauce is plain yogurt, but you can use sour cream if you want. To the yogurt I added a spoonful of mayo, some garlic, fresh horseradish and some salt and pepper … and holy smokes, was it good!

A generous smear of the horseradish sauce on a lightly-toasted bun, topped with thinly-sliced steak, grilled onions and some arugula makes for one seriously delicious steak sandwich!

Grilled Steak & Onion Sandwiches with Creamy Horseradish Sauce

Makes 4 sandwiches

For the Creamy Horseradish Sauce:
½ cup plain yogurt
2 tablespoons mayonnaise
1 tablespoon horseradish
2 cloves garlic, minced
¼ teaspoon salt
¼ teaspoon pepper

For the Steak Sandwiches:
2 (12-16 ounce) sirloin steaks
Your favorite steak seasoning
3 tablespoons olive oil
2 yellow onions, thinly sliced
4 ciabatta buns
Butter, for the buns
Arugula, for topping


  1. Make the horseradish sauce by combining all sauce ingredients and stirring well to combine.  Cover and let sit in refrigerator until ready to use.
  2. Heat grill to medium-high heat.
  3. Season steak with steak seasoning. Lightly brush with 1 tablespoon of olive oil. Let sit at room temperature for 20 minutes.
  4. Meanwhile, toss onions with additional 2 tablespoons olive oil and season them with salt and pepper.
  5. Place onions in a grilling pan or wrap in foil. Place on grill and cook until onions are softened and beginning to caramelize, about 25 minutes.
  6. Once steak has sat at room temperature for 20 minutes, place on grill.
  7. Cook for 4-5 minutes, until steak is golden and has grill marks, and then flip. For medium-rare, cook
    until internal temperature reaches 140 F (another 3-4 minutes); for medium, cook until 150-155 F (another 5-6 minutes); and for medium-well cook until 160-165 F (another 6-7 minutes).  This always depends on the thickness of your steak. To be sure, use a meat thermometer.
  8. Let your steak rest for 3 minutes before slicing.
  9. While steak is resting, butter the buns.
  10. Place bun halves on grill, butter side down, and lightly grill for 1-2 minutes. Keep a close eye on them, as they will burn easily.
  11. Once steak has rested, cut it as thinly as possible.
  12. Place approximately 2 tablespoons of spread on the bottom half of each bun.
  13. Top with steak and onions.
  14. Top with arugula and finally the top half of the bun. Serve and enjoy!
Grilled Steak & Onion Sandwiches with Creamy Horseradish Sauce