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Mushroom and Onion Steakburgers

Published June 20th 2018 Updated December 13th 2023

These mouthwatering open faced Mushroom and Onion Steakburgers are an elegant way to serve a burger for a special meal or as an appetizer. Fresh hoagie rolls are slathered with garlic butter then topped with seasoned ground sirloin and baked until the beef is cooked. Top with sautéed mushrooms and caramelized onions they’re ready to smother with cheese. Place under the broiler until the cheese is gooey and golden. Cut into pieces and serve with dippers as an appetizer, game day treat or a small bites meal.


Easy Open Faced Mushroom and Onion Steakburgers Recipe

These steakburgers are an elevated way to serve hamburgers. They’re served with basil pesto and sundried tomatoes on the side as an entree or starter for a casual soiree. I enjoy serving them both ways, as an appetizer as well as a small bites meal. It’s a sort of a grown-up way to eat an everyday cheeseburger and the buttered, garlicky, cheesy baguette makes it over the top gourmet good! In those moments I don’t have time to grill, or the weather won’t permit, these delectable open faced burgers curb the burger craving spot. Ingredients you’ll need to make Open Faced Mushroom and Onion Steakburgers in the oven:

  • Bread – One 21 inch soft french baguette. Cut in half lengthwise then cut each half into two pieces.
  • Butter – Unsalted butter, softened.
  • Cheese – 10 -12 thick slices of gruyere or cheddar cheese. You could also use mozzarella cheese.
  • Beef – Two pounds of extra-lean ground sirloin.
  • Seasonings – Garlic salt, steak seasoning and steak sauce i.e. A-1 or similar.
  • Binder – One large egg.
  • Mushrooms and Onions – Baby portabella mushrooms, sweet onion, olive oil, balsamic vinegar, fresh thyme leaves, granulated sugar, salt and black pepper.

How To Make Mushroom and Onion Steakburgers

How to Make the Best Open Faced Mushroom and Onion Steakburgers

  • Kitchen tools you’ll need: One large sheet pan, bread knife, measuring cups and spoons, skillet, medium bowl, sharp knife and cutting board.
  • To make these steakburgers you’ll need one long french baguette. Cut it in half lenghtqise then cut each piece into two even pieces.
  • Butter each piece, season with garlic salt and cover with a slice of cheese. The cheese forms an edible glue.
  • In a medium bowl mix together the ground sirloin with the egg, steak sauce and seasonings then spread it onto the bread. Bake per the recipe while you cook the mushrooms and onions on the stovetop.
  • At the end of baking, divide the mushrooms and onions on top of each steakburger and cover with more cheese. Broil until the cheese is golden and bubbly.
  • Please note: The ground beef in this recipe isn’t precooked, it cooks in the oven. Due to This it’s important to use a lean ground beef.
  • The flavor will be directly affected depending on the quality and flavor of the steak seasoning used. Use a good quality brand that you already enjoy or one that’s readily available on the spice aisle. Chicago, Kansas City and Montreal steak seasonings are both easy to come by.
  • You can experiment and use your favorite cheese for this recipe.
  • Use a super sturdy baguette to hold up to the baking process. You could also use ciabatta for this recipe.
  • Mushroom and Onion Steakburgers are best made and eaten fresh. Serve them with basil pesto, sundried tomato pesto, garlic aioli or any flavored mayonnaise for dipping.
  • These burgers can be served as an appetizer or small bite meal.
  • Store Open Faced Mushroom and Onion Steakburgers for up to 3 days chilled in the refrigerator then reheat in the microwave on 50% power or in a 350°F air fryer.

More Easy Burger Recipes to Make

Mushroom and Onion Steakburgers

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Open Faced Mushroom and Onion Steakburgers

Prep Time10 minutes
Cook Time22 minutes
Total Time32 minutes
Course: Appetizer, Main Course
Cuisine: American, Southern
Keyword: mushroom-cheeseburger-recipe, open-faced-mushroom-onion-steakburgers, steakburgers
Servings: 8 servings
Calories: 458kcal
Author: Melissa Sperka


  • 1 21 inch soft french baguette
  • 4 Tbsp unsalted butter softened
  • 1 tsp garlic salt
  • 10-12 thick slices Gruyere or Cheddar cheese cut in half and divided
  • 2 lb extra-lean ground sirloin
  • 1 Tbsp steak sauce i.e. A-1
  • 1 1/2 tsp steak seasoning i.e. Kansas City, Chicago or Montreal use your favorite
  • 1 large egg
  • 2 Tbsp olive oil
  • 1 8 oz container sliced baby portabella
  • 1 large sweet onion thinly sliced
  • 1 Tbsp balsamic vinegar
  • 2 tsp fresh thyme leaves
  • 1/4 tsp sugar
  • salt and black pepper to taste


  • Preheat the oven to 400°F and move the oven rack to the upper 1/3 of the oven. Line a large baking sheet with parchment.
  • Baguettes: Slice baguette in half lengthwise then cut each piece in half again making 4 even oblong pieces. Arrange side by side on the baking sheet. Divide butter between pieces and sprinkle lightly with garlic salt. Arrange half of the cheese slices over the buttered baguette reserving the other half for the top. Set aside.
  • Burgers: In a medium size mixing bowl, mix together ground sirloin, steak sauce, steak seasoning and egg. Mix until fully combined. Divide evenly between the baguettes, spreading to the edges. The meat will be thin.
  • Place burgers into the oven and bake for 20-22 minutes depending on the thickness of the meat.
  • Mushrooms and Onions: Meanwhile, while steakburgers bake, in a large skillet over medium-high heat, cook mushrooms and onions in a couple of drizzles of olive oil for about 10 minutes until golden. Add balsamic vinegar, fresh thyme and sugar. Season with salt and black pepper to your taste.
  • Set the oven temperature to broil and remove steakburgers from the oven. Arrange sauteed mushrooms and onions on top dividing evenly between the four pieces. Cover mushrooms with the remaining slices of cheese. Return to the oven broiling until the cheese melts.
  • Cut each steakburger into 4 equal pieces and serve with an assortment of flavored mayonnaise, pesto or spreads.


  • By moving the oven rack closer to the top element the meat will cook evenly without overcooking the baguette.


Serving: 1serving | Calories: 458kcal | Carbohydrates: 4g | Protein: 23g | Fat: 28g | Saturated Fat: 11g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 12g | Trans Fat: 1g | Cholesterol: 117mg | Sodium: 414mg | Potassium: 409mg | Fiber: 1g | Sugar: 3g | Vitamin A: 260IU | Vitamin C: 3mg | Calcium: 50mg | Iron: 3mg
Tried this recipe?Mention @melissassk or tag #melissassk!


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