Portobello Mushroom Sandwich

This Portobello Mushroom Sandwich is the BEST! Big, rich and meaty this vegetarian burger will make you a believer of a meatless meal! It can be made in the slow cooker or Instant Pot and it's super easy.

Course Vegetarian
Cuisine American
Prep Time 15 minutes
Cook Time 4 hours
Total Time 4 hours 15 minutes
Servings 2 sandwiches
Calories 712 kcal
Author Souper Chef Deb


  • 2 portobello mushrooms
  • 1 16 oz package pre-sliced mushroom
  • 1 red bell pepper
  • 1/2 red onion
  • 1/2 cup bbq sauce - use your favorite
  • 1 teaspoon salt
  • 1/2 teaspoon pepper
  • healthy pinch red pepper flakes
  • Coleslaw
  • 1/2 head cabbage
  • 2 carrots
  • 1/2 red onion
  • 1/2 cup mayonnaise
  • 2 tablespoons cider vinegar
  • 2 tablespoons honey
  • salt and pepper to taste


  1. Clean the portobello mushrooms, remove the stem & fins, place in the slow cooker. Top with the pre-sliced mushrooms.
  2. Slice the bell pepper, remove the seeds and slice into strips. Remove the outer peel from the onion and slice into strips. Place into the slow cooker with the mushrooms.
  3. Season the vegetables with salt, pepper & red pepper flakes, top with bbq sauce. Put the lid on the slow cooker & cook on high for 4 hours or low for 6.
  4. While the meal is cooking, make the cole slow. Thinly slice the cabbage, clean & shred the carrots (I use a box grater.), thinly slice the onions, place in a large bowl.
  5. Mix the coleslaw dressing together - it will be quite thick, but that's how you want it. Mix the dressing with the vegetables, refrigerate until ready to use.
  6. Toast the burger buns.
  7. Assemble and enjoy!

Nutrition Facts
Portobello Mushroom Sandwich
Amount Per Serving
Calories 712 Calories from Fat 387
% Daily Value*
Total Fat 43g 66%
Saturated Fat 6g 30%
Cholesterol 23mg 8%
Sodium 2349mg 98%
Potassium 1258mg 36%
Total Carbohydrates 78g 26%
Dietary Fiber 11g 44%
Sugars 59g
Protein 7g 14%
Vitamin A 249.5%
Vitamin C 202.6%
Calcium 14.7%
Iron 13%
* Percent Daily Values are based on a 2000 calorie diet.