Portobello Mushroom Sandwich
May contain affiliate links. See our disclosure policy.
Craft an epic Portobello Mushroom Sandwich, loaded with balsamic marinated portabella mushrooms, Swiss cheese, roasted red peppers, microgreens, and a secret special sauce! This super satisfying mushroom burger is perfect for a quick weeknight dinner or cookout!
The Anatomy of an Epic Portobello Sandwich

Table of Contents
If we ever opened a NeighborFood restaurant, our specialty would be sandwiches. Sandwiches are quick to make, but deliver BIG in flavor. They can be hot or cold, meaty or vegetarian, healthy or a worthwhile splurge. This Vegetarian Mushroom Sandwich falls in the warm and healthy (but oh-so- satisfying) camp.
Over the years, we’ve experimented with dozens of different sandwich recipes, and we’ve learned a few things along the way. From a stack of gloriously gooey Apple Brie Grilled Cheese to the deceptively simple classic Scrambled Egg Sandwich, there are four elements that take any sandwich from good to great.
- Good bread– This is not a place to skimp. We’re talking chewy ciabatta, herby focaccia, a puffy sweet Brioche. A great sandwich starts with great bread.
- Special sauce– Plain mayo is fine, but all the best sandwiches have a special sauce. Whether it’s homemade pesto or Big Mac sauce or the chipotle mayo we use on our Turkey Avocado Sandwich, a secret sauce adds creaminess and prevents the sandwich from being dry.
- Layers of filling– Whether you’re making a vegetarian mushroom sandwich or a meaty Skirt Steak Sandwich, you’ll want to layer different flavors and textures together. Add crisp lettuce or microgreens or pile on juicy tomato and crunchy radish. The options are endless!
- Cheese– Sliced cheese, shredded cheese, or cream cheese, this is an essential ingredient in all of our sandwich recipes.
Today, we’ll use the four building blocks of a great sandwich to make the ultimate Grilled Portobello Mushroom Sandwich. This sandwich delivers big, bold flavors in a package that will be loved by meat eaters and vegetarians alike.
Key Ingredients

- Bread– A soft, puffy Brioche roll is the perfect size and shape for a portobello mushroom burger.
- Mayo + Lemon + Garlic + Herbs– A bright garlic aioli is the secret sauce that makes this sandwich pop.
- Portabella Mushrooms– Portabello mushrooms are a large variety of mushrooms with a rich, umami flavor. Their bigger size makes them perfect for stuffing, grilling, and in plant based burgers. They can also be chopped up and used in recipes like Parmesan Leek and Mushroom Pasta or Creamy Mushroom Soup.
- Balsamic Vinegar + Garlic + Soy Sauce + Lemon Juice– A flavor packed savory marinade for the mushrooms with a hint of sweetness and citrus.
- Swiss Cheese– Melty, gooey Swiss cheese pairs beautifully with mushrooms and makes this sandwich extra satisfying. Swiss and other cheeses like mozzarella and cheddar are also a great source of protein for a plant based sandwich. I used Guggisberg Baby Swiss for this recipe, but you could also substitute gruyere on another cheese of your choice.
- Greens– We use both lettuce and microgreens to add some fresh green goodness to the sandwiches.
For a full list of ingredient amounts, visit the recipe card below.
How to Buy, Store, and Clean Portobello Mushrooms
When shopping for portobellos (or any mushroom, really), look for caps that are firm and dry, without any slimy or mottled spots. Store the mushrooms in the container you bought them in until you’re ready to cook them.
Use a slightly damp paper towel to wipe away any dirt from the surface of the mushrooms before cooking. You’ll also want to remove the thick, woody stem. I find the easiest way to remove the stem is to place a finger on either side of the stem, then use your other hand to gently work the stem back and forth until it pops out.

How to Grill Portobella Mushroom Sandwich

Step 1: Marinate the mushrooms. Whisk together olive oil, garlic, balsamic vinegar, lemon juice, soy sauce, and salt and pepper. Pour over the mushrooms. Cover and refrigerate at least 30 minutes or up to 12 hours.
Step 2: Prep the grill. Clean and oil the grill grates, either by rubbing with an oil soaked paper towel or spraying with cooking spray. Preheat to medium heat (375-400 degrees).

Step 3: Grill. Place the mushrooms directly on the grill grates cap side down, and grill undisturbed for 3-4 minutes per side, or until the mushrooms are softened and take on a rich, brown color. Add cheese slices for the last minute.

Step 4: Assemble. Spread the aioli on both sides of the buns. Top with lettuce, then mushrooms, roasted red peppers, and microgreens. Serve.
Storage and Make Ahead Instructions
- The marinade and the aioli can be made up to 3 days in advance and stored in the fridge.
- Mushrooms can be marinated up to 12 hours.
- Leftover mushrooms keep well in an airtight container in the fridge for up 4 days.
- Reheat mushrooms on the stove top or in the microwave.

Variations + Tips
- Make them vegan! For a vegan mushroom sandwich, swap the mayo for eggless mayo, and omit the cheese or use vegan cheese.
- Experiment with toppings– These would also be lovely with sun dried tomatoes, avocado, red onions, spinach, or arugula. Goat cheese would be absolutely fabulous, or you could add a little funk with blue cheese.
- Pair dairy foods with plants to create a nutritional powerhouse, including vital nutrients like calcium, vitamin D, potassium, and fiber. I use this combo in the Best Ever Veggie Sandwiches as well as in this Veggie Pizza, Caprese Panini, and Roasted Broccoli Cheese Casserole.
- Use leftover aioli on Grilled Burgers or in Roasted Red Pepper Turkey Wraps.
- Love the combination of mushroom and Swiss, but miss the meat? Try these Mushroom Swiss Burgers!
FAQs
Mushrooms soak up a marinade quite quickly. I prefer to marinate mushrooms for at least 30 minutes for the best flavor, but they can go as long as 12 hours. Toss together the marinade in the morning, and it’ll be ready for you at dinner time! Be sure the marinade covers both sides of the mushroom. I prefer to marinate them gill side up, so the marinade can soak into it.
Yes! Heat a grill pan over medium high heat. Add the mushrooms, cooking each side for 3-4 minutes, or until well seared.

More Vegetarian Sandwich Recipes to Enjoy
Who says you need meat to make a great sandwich? Try these amazing plant based and vegetarian sandwiches next time you need a sandwich fix!
- Best Ever Veggie Sandwiches
- Roasted Portobello Mushroom Veggie Sandwich
- Cucumber Sandwiches
- Swiss and Mushroom Grilled Cheese
- Scrambled Egg Sandwiches
- Ultimate Beet and Bean Veggie Burgers

Portobello Mushroom Sandwich
Ingredients
For the mushrooms:
- 4 portobello mushroom caps (cleaned, stems removed)
- 1/4 cup balsamic vinegar
- 2 Tablespoons olive oil
- 1 Tablespoon lemon juice
- 1 Tablespoon soy sauce
- 3 cloves garlic (minced)
- 3/4 teaspoon Kosher salt
- 1/2 teaspoon ground black pepper
For the aioli:
- 1/2 cup mayonnaise
- 1/4 cup chopped chives
- 1 teaspoon dijon mustard
- 1 clove garlic (minced)
- Squeeze of lemon juice
- Salt (to taste)
For the sandwiches:
- 4 slices Swiss cheese
- 4 brioche buns
- 1 cup mixed greens, microgreens, and/or sprouts
- 6 ounces jarred roasted red bell peppers (sliced)
Instructions
Marinate the mushrooms:
- In a glass measuring cup, whisk together the balsamic, olive oil, lemon juice, soy sauce, and salt and pepper. Place the mushrooms in a zip lock bag or shallow dish and pour the marinade over the top and undersides of the mushrooms. Cover and refrigerate, marinating for at least 30 minutes or up to 12 hours.
Make the aioli:
- Combine the mayo, chives, dijon, garlic, and lemon in a measuring cup.whis together. Taste and season with salt as needed.
Grill the mushrooms:
- Start with clean and oiled grates. Preheat the grill over medium high heat (400-425 degrees). Use tongs to transfer the mushrooms directly to the grill. Grill undisturbed for 3-4 minutes per side, or until mushrooms take on a rich, brown color. Place cheese slices on the mushrooms for the last minute of cooking time.
Serve:
- Spread each side of the brioche bun with the prepared aioli. Layer with the greens, grilled portabellas and cheese, sliced red peppers, then more greens or sprouts. Sandwich together and enjoy!
Notes
- To make the sandwich vegan, use eggless mayo and omit the cheese.
- To pan fry the mushrooms, brush a grill pan with a little oil, then heat over medium high heat. Add the mushrooms and cook undisturbed for 3-4 minutes per side or until mushrooms take on a rich brown color. Place cheese slices on the mushrooms for the last minute of cooking time.
- Leftover aioli and mushrooms will keep well stored in a sealed container in the fridge for about 4 days.
This sandwich was absolutely delicious!! I had been looking for a really good portobello mushroom sandwhich/burger recipe that I could whip up when I’m in the mood for a burger. This really hit the spot!! The flavor was absolutely delicious!! The second time I made it, I added avocadoes and that just made it even more gourmet!! Thanks so much for this recipe. If you’re considering making this, I highly encourage you to make it. You will not be disappointed!!