Portobello Mushroom Sandwich Recipe

Brie Norris | Toaster Oven Love Updated

Loaded with savory roasted vegetables and melted provolone cheese, this Portobello Mushroom Sandwich is so satisfying even meat eaters will love it. Perfect for your next Meatless Monday!

We’ve shared a lot of sandwich recipes on the site but I think this Portobello Mushroom Sandwich might be my all-time favorite. In the last month, Tim and I have made it over 5 times and we’re still not sick of it!

Portobello Mushroom Sandwich Photo

A few things that make this a great weeknight dinner recipe:

  1. Everything is toasted and roasted in the toaster oven, so it’s EASY to throw together.
  2. Lots of yummy veggies: juicy portobello mushroom, sweet roasted onion, and crisp bell pepper. (I love the slight bitterness of green peppers but you can use a sweeter red, orange, or yellow pepper instead.) 
  3. It’s loaded with a CRAZY amount of salty, earthy, rich umami flavor.
Portobello Mushroom Sandwich Picture

If you’ve tried one of our other vegetarian sandwiches, like this popular Roasted Red Pepper, Carrot and Hummus Sandwich or a Grilled Cheese with Apple and Havarti, then you know we take our sandwich game pretty seriously.

And these cheesy mushroom melts are no exception. They’re incredibly delicious and you NEED to make them tonight.

File 3 - Portobello Mushroom Sandwich

How to Make A Portobello Mushroom Sandwich

STEP 1: Toast Your Rolls While You Preheat

Start by lowering the rack in your toaster oven to the bottom position, place your rolls (unsplit) on the rack and preheat to 425°F on the BAKE setting.

One of the best parts of this sandwich is the rolls - they’re crunchy and toasted outside but soft and warm inside. To achieve this awesomeness, just warm and toast the rolls while your little oven preheats.

If your toaster oven only has a traditional temperature dial, set a timer for about 5 minutes.

Portobello Mushroom Sandwich Image

STEP 2: Make The Marinade 

The quick marinade for the vegetables is simple: olive oil, balsamic vinegar, soy sauce, and a few spices. To make it, dump everything in a large bowl and whisk together.

Add the mushrooms to the marinade solo, this gives them a chance to soak up most of it first. Then toss in the pepper and onion slices.

Lastly, rub a rimmed sheet pan with a little oil and pour the veggies onto it.

Portobello Mushroom Sandwich Pic

STEP 3: Roast The Vegetables

Right about now, the toaster oven should beep that it’s ready. Remove the rolls, set them aside, and add the vegetables.

Stir the pan once or twice while it cooks. Around the 7 minute mark, the mushrooms will begin to release a lot of liquids and your house will start smelling very good.

After about 15 to 18 minutes a little of the liquid will remain but the onions, mushrooms, and peppers will be brown on the edges and have a delicious tender-yet-toothy texture.

File 1 - Portobello Mushroom Sandwich

STEP 4: Get Melty

Put on a pair of oven mitts and carefully remove the hot pan. Use a spatula to scooch the roasted vegetables into two piles and top each one with a slice of smoky provolone cheese.

To melt the cheese, return the pan to the toaster oven for 2 to 3 minutes.

File 2 - Portobello Mushroom Sandwich

STEP 5: Assemble Your “Meaty” Meatless Sandwiches

Split the rolls in half and scoop the filling into each one. For a little spicy kick, sprinkle on a pinch of red pepper flakes. Then grab a few napkins, and enjoy!

Cooking For One? Toast a single roll and save half the roasted vegetables. You can use the leftover veggies to make a toaster oven frittata, throw them on a veggie hummus flatbread, or whip up another Portobello Mushroom Sandwich for lunch or dinner the next day.

File 4 - Portobello Mushroom Sandwich

Planning a dinner party and need some inspiration?

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Portobello Mushroom Sandwich Recipe

    2 Servings


  • 2 Sandwich Rolls
  • 2 teaspoons Olive Oil, divided
  • 1 tablespoon Balsamic Vinegar
  • 2 teaspoons Low Sodium Soy Sauce
  • 1/2 teaspoon Dried Oregano
  • 1/4 teaspoon Garlic Powder
  • 1/4 teaspoon Black Pepper
  • 1 large Portobello Mushroom, thinly sliced
  • 1 small Bell Pepper, seeded and thinly sliced
  • 1/2 small Onion, thinly sliced
  • 2 slices Provolone Cheese


  1. Adjust the cooking rack to the bottom position and preheat your toaster oven to 425°F. While the toaster oven preheats, place the sandwich rolls inside to warm and toast. 
  2. Rub a rimmed sheet pan with 1 teaspoon of the oil.
  3. In a large bowl, whisk together the remaining 1 teaspoon olive oil, balsamic vinegar, soy sauce, oregano, garlic powder, and pepper. Add mushrooms and stir to coat well with the sauce. Stir in bell pepper and onion. Pour vegetables onto the prepared pan.
  4. Once the oven has preheated, remove sandwich rolls and add vegetables.
  5. Roast vegetables, stirring occasionally, until fork tender, about 15 to 18 minutes minutes.
  6. Carefully remove the pan and divide the veggies into two piles on the pan. Top each pile with a slice of provolone cheese. Return pan to the toaster oven and cook until the cheese is melted about 2 to 3 minutes.
  7. Split the rolls in half, scoop the filling into each one, and dig in!


Cooking Method:
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Related Recipes:
Toaster Oven Cooking Recipes, Sandwich Recipes, Mushroom Recipes, Pepper Recipes, Cheese Recipes, Roasted Recipes, Easy Lunch Recipes, Lunch Recipes, Easy Dinner Recipes, Vegetarian Recipes
Recipe Yields:
2 sandwiches
Prep Time:
Cook Time:
Total Time:
Related Post:
Author: Brie Norris
Recipe Yields: 2 sandwiches
Prep Time: 15 minutes
Cook Time: 20 minutes
Total Time: 35 minutes

Nutrition Facts

Serving Size 1 sandwich
Servings Per Recipe 2

Amount Per Serving
Calories from Fat 120
Calories 358

% Daily Value*
Total Fat 15g
  Saturated Fat 6g
Sodium 424mg
Total Carbohydrate 38g
  Dietary Fiber 2g
  Sugars 14g
Protein 14g

* Percent Daily Value are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.
** Nutrition Facts are estimated based on ingredients and data provided by Fat Secret. Please consult a doctor if you have special dietary needs.
Brie Norris

About Brie

Brie loves her toaster oven so much, she started Toaster Oven Love. We're so excited to see all the yummy things she comes up with as our Toaster Oven Cooking fanatic.