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Vegetarian Stuffed Portobello Mushrooms (Grill or Bake)

A delicious main or side dish, these vegetarian stuffed portobello mushrooms, filled with fresh vegetables, herbs and cheese, are a wonderful change of pace.

When I talk about ‘stuffed’ in this recipe, I mean STUFFED. These monsters hold a lot. We load them with healthy fresh chopped spinach, butternut squash, cheese, green onions, oregano, tomatoes and Panko. Really yummy!

grilled stuffed mushroom cap on cutting board.

This stuffed portobella recipe was inspired by 3 great recipes in the New York Times, Cooking Light and All Recipes with a few additional tweaks.  

Bottom line: The result is a tasty, healthy and satisfying vegetarian main dish or side dish where meat lovers (like me) don’t actually miss the meat. It’s an easy recipe for a weeknight dinner – grilled or baked.

Ingredients – tailored to your taste

portobello mushroom caps, spinach, butternut squash spirals, cheeses, balsamic vinegar, oil, chopped tomatoes, garlic. oregano.
Ingredients: Large portobello caps, panko, spinach, tomatoes, garlic, Parmesan cheese, spiralized butternut squash, balsamic vinegar, olive oil, green onions (missing), oregano (ignore the butter!)

Portobello mushrooms: These are large, meaty mushrooms with a savory, umami flavor that are perfect for holding a stuffing due to their large caps.

Stuffing: I use a mixture of spinach, tomatoes, panko breadcrumbs, mozzarella and parmesan cheese, spiralized butternut squash, garlic, green onions and oregano.

Marinade: I marinate the mushrooms with a good quality balsamic vinegar, olive oil and a touch of Dijon mustard to add extra flavor.

Variations and substitutes

  • Veggies: Try bell pepper, canned black beans or white beans. You can certainly skip the spiralized butternut squash if you want, although it does add a nice bit of texture. Or try replacing the regular tomatoes with homemade fire roasted tomatoes.
  • Cheese: Instead of mozzarella, try goat cheese, feta cheese, gruyere or Emmenthal
  • Herbs: Instead of oregano or thyme, try fresh tarragon or chives. You can also use Italian seasoning or other dried herbs (1 tablespoon fresh = 1 teaspoon dried, a 3:1 ratio)
  • No grill? These meaty portobello mushrooms can easily be baked in the oven. at 425F/218C on a baking sheet for about 8-10 minutes.

Step by step instructions

one mushroom cap cleaned of gills, one with gills still on.
Wipe top of mushroom caps with damp paper towels. Scrape gills from inside of the mushroom with a spoon.
mushroom caps brushed with marinade on cutting board.
Marinate mushrooms for 20-30 minutes (shortcut: use bottled dressing)
stuffing ingredients in bowl.
Make veggie cheese herb stuffing
uncooked mushroom caps stuffed on tray.
Divide veggie filling among mushrooms Top with extra cheese.
one mushroom cap cooking on grill.
Grill mushrooms for 6-7 minutes (or see how to bake instead)
grilled stuffed mushroom cap on cutting board.
cut open stuffed mushroom cap on cutting board.

TIP

You can alter the veggies, BUT:

  • don’t use vegetables with a high water content like zucchini as they will make the stuffing soggy.
  • use fast cooking or very finely chopped vegetables as the cooking time is short.

Shortcuts

  • Buy pre-spiralized butternut squash or leave it out altogether.
  • Buy pre-washed fresh baby spinach
  • Instead of grating the cheese buy it pre shredded.
  • Substitute fresh garlic with garlic from the jar or frozen cubes.
  • Marinate the mushrooms in a store-bought Balsamic or Italian salad dressing.

Make Ahead 

  • The whole thing can be prepared well in advance and grilled just before serving.
  • Or, complete the dish, then just before serving, rewarm under the broiler for 2 minutes.

What to serve with stuffed portobellos

If you’re serving the stuffed mushrooms as a main dish, here are a few good sides: purple cabbage slaw, flat green beans (charred) and citrus salad with greens. Jenna, the vegetarian kook, likes to top them with a bit or marinara sauce or salsa.

As a side dish, the mushrooms pair really well with: flank steak, cedar planked chicken, easy maple lime salmon, smoked chicken thighs (no smoker needed) and juicy grilled pork chops.

Or check out our summer Sunday dinner ideas for other options.

FAQs on portobello mushrooms

What are portobello mushrooms?

Like all mushrooms, portabella mushrooms are actually fungi (not vegetable. plant or animal. They are the same species as white button mushrooms and cremini mushrooms, but are much larger and can be as big as 6 inches/15 cm in diameter.

Should I remove the gills on the portobello mushrooms before cooking?

Although gills are edible, it’s a good idea to remove the gills on portobello mushrooms before cooking them as they can make the stuffing and mushrooms soggy. They are easy to scrape off with a spoon.

How should portobello mushrooms be stored?

According to WebMD, fresh portabella mushrooms should be stored in the fridge in their original container or a paper bag, not at room temperature where they may grow bacteria. 

grilled stuffed mushroom cap on cutting board.

Love mushrooms? Then try…

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grilled stuffed mushroom cap on cutting board.
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Veggie Stuffed Portobello Mushrooms

A delicious main or side dish, these vegetarian stuffed portobello mushrooms, filled with fresh vegetables, herbs and cheese, are a wonderful change of pace. When I talk about 'stuffed' in this recipe, I mean STUFFED!
Prep Time30 minutes
Cook Time6 minutes
Total Time36 minutes
Course: Main Course, Side Dish
Cuisine: American
Diet: Low Calorie
Servings: 3 mains (or 6 sides)

Ingredients

  • 6 large Portobello mushrooms (mushroom stems removed)

Marinade

  • 2 tablespoons olive oil
  • 2 tablespoons good balsamic vinegar
  • 1 teaspoon Dijon mustard

Stuffing, Note 1

  • 2/3 cup Panko (Japanese) bread crumbs
  • 3/4 cup shredded Mozarella cheese (or Emmenthal), divided (optional: additional grated Parmesan cheese)
  • 3 tablespoon finely chopped green onions or chives
  • 1 tablespoon fresh chopped oregano (or thyme)
  • 1/2 cup chopped tomato, juice squeezed out
  • 2 cups fresh baby spinach, roughly chopped
  • 1 cup spiralized butternut squash (OPTIONAL)
  • 2 teaspoons garlic, minced (2 garlic cloves) or 1/4 tsp garlic powder
  • 1/2 teaspoon each salt and black pepper (or to taste)

Instructions

  • PREPARE AND MARINATE MUSHROOMS: Wipe/clean top of portobello mushroom caps with a damp paper towel. Using a spoon, gently scrape out the black gills in the inner side of the mushroom caps and discard. Mix together marinade ingredients, brush over top and bottom of mushrooms, then set aside for 20-30 minutes to marinate while you prepare the stuffing. Shortcut: use a bottled salad dressing instead of marinade e.g. Italian or balsamic.
  • PREPARE GRILL: Spray grill with oil or wipe grill with an oil soaked paper towel. Heat BBQ grill to medium high heat. Note 2 (to bake)
  • PREPARE STUFFING AND STUFF MUSHROOMS: In a medium bowl, combine all stuffing ingredients (leaving 1/4 cup of mozzarella cheese for topping). Taste and adjust seasonings. Spoon stuffing into cavity of the 6 mushroom caps, pressing down slightly to adhere. Sprinkle on remaining 1/4 cup mozzarella. If desired, sprinkle on some Parmesan cheese too.
  • GRILL AND SERVE: Place mushrooms on grill, stuffing side up. Close lid and cook about 6-7 minutes. Serve immediately.

Recipe Notes

  1. Variations
    • Veggies: Keep in mind that the cook time is short, so you need to use vegetables that require minimal cooking time.
      • Red peppers, canned black or white beans (drained and rinsed) would work fine for example.  
      •  I would not suggest using high water-content vegetables such as zucchini, however, as the stuffing and mushrooms may become soggy.
    • Cheese: Instead of mozzarella, try goat cheese, gruyere or Emmenthal. For a vegan version, use vegan cheese or nutritional yeast. 
    • Herbs and spices: Instead of oregano or thyme, try fresh tarragon, fresh basil or chives. You can also use dried Italian seasoning or other dried herbs (1 tablespoon fresh = 1 teaspoon dried, a 3:1 ratio). And feel free to add a pinch of cayenne pepper if you like heat. 
  2. To Bake instead of grill: If you don’t have a grill, the stuffed portobello mushrooms can be baked in a 425F/218C oven for about 10-12 minutes on a baking sheet.
  3. To Make Ahead: Complete the dish. Let mushrooms sit until needed. Then rewarm under the broiler for 2 minutes. Or, prepare everything ahead including stuffing the mushrooms, then grill just before serving. Leftovers can be stored in an airtight container for 3 days and rewarmed in the oven. 
 
Nutrition values are estimates for 2 stuffed mushrooms per serving. If using as a side dish (1 mushroom per person), nutrition values would be cut in half. 

Nutrition

Calories: 306kcal | Carbohydrates: 28g | Protein: 13g | Fat: 17g | Saturated Fat: 5g | Cholesterol: 22mg | Sodium: 718mg | Potassium: 1043mg | Fiber: 5g | Sugar: 9g | Vitamin A: 7320IU | Vitamin C: 21mg | Calcium: 248mg | Iron: 3mg
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