The key to a great weeknight meal is something that’s easy to prep ahead of time and comes together quickly. These open-faced sandwiches fit the bill, with grilled flank steak on crunchy bread that’s topped with spicy arugula, a few pickled red onions and a tasty parmesan mustard sauce giving you the ultimate easy dinner solution.

Three open faced sandwiches topped with grilled flank steak, bright pickled red onions and parmesan sauce

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I don’t eat a lot of steak but when I do it’s nearly always tenderloin so I’ve been wanting to do a recipe with a different type of steak. Enter the open-faced grilled steak sandwich!

These steak sandwiches make an excellent light summer or early fall dinner and are also a big hit as a party appetizer. Not doing carbs this week…or ever? No problem – ditch the bread and add a bit more arugula. Now you’ve got a mini steak salad!

But assuming you are into bread, pick a nice crusty bread and toast it just a little bit before you assemble the sandwiches. Sometimes I even scoop out a little bit of the center of the bread to make it easier for the toppings to stay on the bread.

Close up of an open faced steak sandwich on crusty bread topped with bright pink pickled onions

Meal Prep Tips

If you want to start these as part of your weekly meal prep you can make the marinade the night before or even a day or two ahead of time and then throw the flank steak in the marinade before you leave for work. When you get home, just fire up your grill and take the steak out of the refrigerator. Grill and enjoy.

You can also grill the steak a day or two ahead of time and serve these as cold steak sandwiches. I’ve tried them that way a couple of times and they are delicious!

Both the pickled onions and the parmesan mustard sauce can also be made ahead of time so this recipe is a great one to add to your weekly meal prep plans.

Pickling red onion is really easy and I typically keep a jar of them in my refrigerator. I normally use this recipe from Gimme Some Oven but there are tons of options out there, all with slight variations, so give a couple a try until you find your favorite.

For some other easy weeknight meal ideas check out these Stuffed Grilled Peppers or this Sticky Asian Grilled Chicken.

things you might want for this recipe

Weber iGrill 3 – If you have a Weber grill that is compatible with this thermometer I highly recommend investing in one. I’ve tested it out on this flank steak as well as burgers and chicken and it is spot on. No more guessing when food is done, just set the temperature on the app and your phone will tell you when to take the food off the grill!!