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Overhead view of three portobello subs on a wood cutting board.

Portobello Mushroom and Spinach Subs

You'll never miss the meat in these hearty and savory subs prepared in 30 minutes!
Prep Time 20 minutes
Cook Time 10 minutes
Total Time 30 minutes
Servings 4 subs


  • 1 loaf baguette about 7 ounces
  • ¼ cup red wine vinegar
  • 1 tablespoon Worcestershire sauce
  • 2 tablespoons spicy mustard
  • 1 tablespoon minced fresh garlic
  • ½ cup extra virgin olive oil
  • 2 (6 ounce) packages portobello mushrooms wiped clean and debris removed with a damp towel, then cut into about 2 inch pieces
  • ½ cup thinly sliced red onion
  • ¼ teaspoon salt more or less, to taste
  • ¼ teaspoon black pepper more or less, to taste
  • 1 (5 ounce) package baby spinach roughly chopped
  • ½ cup shredded mozzarella cheese more or less, to taste


  • Preheat your oven to 350 degrees F. Slice baguette evenly into 4 slices. Slice vertically across each top and hollow each slice out, pulling out the bread inside. Set aside.
  • In a medium bowl, whisk red wine vinegar, Worcestershire sauce, mustard, garlic and olive oil.
  • Place mushrooms and red onion slices in a large baking dish and pour marinade over. Stir and/or toss to coat mushrooms and red onions evenly. Season with salt and pepper and set aside.
  • Transfer mushrooms and red onions in their marinade to a large skillet over medium-high heat (keep baking dish to transfer mushroom/onion mixture back into). Cook over medium-high heat for 5 to 6 minutes, stirring constantly, or until mushrooms are tender.
  • Transfer mushrooms and onions back into marinade dish. Add fresh chopped spinach and stir well to combine and coat spinach as evenly as possible. Spinach will wilt while your baguette is heating.
  • Place baguette slices onto a baking sheet and bake for approximately 5 minutes. Remove from oven and carefully stuff each baguette piece with mixture and top with shredded cheese. Serve immediately.