Portobello Burgers with Roasted Red Peppers, Mozzarella, and Avocado

Portobello Burgers with roasted red peppers, melted mozzarella cheese, and sliced avocado make the best vegetarian burger.

238 CAL 32g CARBS 10g FAT 10g PROTEIN

These easy Portobello Mushroom Burgers are packed with flavor and can be made on the grill, in the oven, or stovetop. Serve them with some Crispy Turnip Fries or Grilled Cauliflower for a delicious, healthy meal.

Although it's hard to tell with the abundance of recipes featuring meat these days, back in the day I was a vegetarian. In fact, I was a vegetarian for almost ten years. During that time, this recipe was something I made all the time. Roasted or grilled portobello mushroom caps, roasted red peppers, basil, fresh mozzarella, and a touch of avocado really makes a killer sandwich.

The "meatiness" of the mushrooms makes this more than your average veggie burger, and gives it that perfect texture that you want in a faux-burger. The roasted red peppers are a little tangy and a little sweet and smoky, for an added depth of flavor. And then the mozzarella — well, that's just because you have to have cheese on your burger, and what goes better than mozzarella on these burgers? Almost nothing, that's what.

To keep the calories low, I often serve this on reduced-calorie bread, but you could use any bread you like. A crunchy French roll or a hearty wheat bread both make delicious sandwiches.

Portobello burger with roasted red peppers, mozzarella, and avocado.

Ways to Serve Portabello Burgers

In addition to a roll or a regular bun, I like to mix up how I serve these in other ways.

  • Try a sandwich slim or bagel slim to cut carbs and calories but not the taste.
  • Add the burgers to lettuce and make wraps. If they don't fit, try slicing the mushrooms in half.
  • Add the burgers over a bed of low-carb or high-fiber spaghetti or other pasta.
  • Try adding these over veggie noodles or zoodles.
  • If your portobellos are large, you can cut them into thirds or fourths and make portobello burger sliders.
  • These are great just by themselves — no buns necessary.
  • How about a veggie burger bowl? Like a deconstructed burger in a bowl. Add a grain like brown rice or quinoa if you like.

What goes good on a portobellow veggie burger?

You know what goes good on veggie burgers? Believe it or not, more veggies! And condiments! And, of course, sauces. Just like a regular burger.

  • Lettuce: iceburg, bibb, green or red leaf, or romaine all make great toppers for burgers.
  • Onions! Red or yellow — whatever is your preference.
  • On that note, how about some pickled onions?
  • If you like your food spicy, try adding some chipotle sauce or chipotles in adobo.
  • Kick up the heat even more with some sliced jalapeno. Try them pickled if you want hot but not too hot.
  • A corn salsa would pair nicely with these burgers as well.
  • Tomatoes — heirloom or otherwise, add a big, meaty piece of tomato to that burger.
  • Try some vegetarian bacon if you want a little crispy bacon flavor but still want to keep it vegetarian.
  • Pickles! Don't knock it until you try it. Pickles go on everything!
  • A slice of avocado would be delish.
  • Try some olive oil mayo, honey mustard, or Dijon mustard as a topping on your burger.
  • Better yet, try marinara sauce or pesto if you want to give it some Italian flavoring.
  • Add fresh herbs to the top of your burger like — basil, cilantro, arugula, or some thyme.

Portobello Mushroom Burgers with mozzarella, red peppers, and avocado.

What are the best mushrooms for veggie burgers?

For me, I like the portobellos because they are basically already a veggie burger without having to do much with them at all. If you like, you could also try some baby bellas, cremini, or white button, though of course this will be more like eating sauteed mushrooms on a bun versus having an actual burger-like patty.

Are veggie burgers better for you than beef burgers?

Like everything else in life, that depends. Are you piling your veggie burgers high with mayo, heavy cream sauces, or cheeses? Are you cooking them in unhealthy oils? If your answer is "yes" then no, they're probably not any better for you than a beef burger.

However, a burger made with extra lean beef has less saturated fat than a typical burger and could be leaner if you aren't junking it up with all kinds of unhealthy toppings. A better meat option would be to make a burger out of ground chicken, turkey, tuna, or salmon.

If it's a big, greasy beef burger you want though, try halving your portion sizes or going for a slider-size. You get what you want, without adding extra calories.

The Recipe
Portobello burger with red peppers, mozzarella, avocado, and red onion on a burger bun.

Portobello Burgers with Roasted Red Peppers, Mozzarella, and Avocado

238 CAL 32g CARBS 10g FAT 10g PROTEIN
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  • 4 portobello mushrooms
  • 2 tbsp. balsamic vinegar
  • 1/2 tbsp. olive oil
  • 1/2 tsp. oregano
  • 1/2 tsp. garlic powder
  • Salt and pepper
  • 1 tomato
  • 4 roasted red peppers
  • 4 reduced calorie hamburger rolls
  • 1/2 avocado
  • 1/2 red onion
  • 1/2 cup basil
  • 2 oz. fresh mozzarella

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Oven option: Preheat the oven to 400 degrees. Brush the mushrooms with balsamic and olive oil. Sprinkle with oregano, garlic, salt, and pepper. Roast for 10 minutes, flip and roast for 5 more minutes. Top with roasted red peppers and fresh mozzarella and cook until melted, about 5 minutes.


Grill option: Brush the mushrooms with balsamic and olive oil. Sprinkle with oregano, garlic, salt, and pepper. Grill for 5 minutes per side. Top with roasted red peppers and fresh mozzarella and cook until melted, about 2 minutes.


Serve on toasted rolls with tomato, roasted red pepper, 1/8 avocado, red onion, and fresh basil.

Nutritional Facts
Serving Size: 1 burger
Amount Per Serving
Calories 238
Calories from Fat 87
% Daily Value *
Total Fat 10g
Saturated Fat 3g
Monounsaturated Fat 0g
Polyunsaturated Fat 0g
Cholesterol 11mg
Sodium 225mg
Total Carbohydrate 32g
Dietary Fiber 7g
Sugars 10g
Protein 10g

* Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.

The Nutritional Values provided are estimates only and may vary based on the preparation method.

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About the author Meet Kristen McCaffrey
Hi, I’m the cookbook author, recipe developer, and food enthusiast behind Slender Kitchen. I am obsessed with making healthy food that is easy to prepare and absolutely delicious. Meal planning is my secret weapon and I hope I can make meal time easier for you with our tried and tested recipes and foolproof meal plans. Learn More
On Portobello Burgers with Roasted Red Peppers, Mozzarella, and Avocado
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February 12, 2023 - 11:55
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Thank you for a great recipe with lots of add-in ideas and flexibility! We are in Mexico, and used portobellos, manchego, turkey chorizo, avacado, cilantro, and fire roasted peppers and onions on our burgers. Delicious!
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Megan Eaton
March 20, 2016 - 19:06
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I used the grilling option and it was excellent! I loved the flavors that were infused into the mushrooms! Definitely worth repeating!
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