Instructions

• Preheat oven to 400°F.
• Wipe the mushrooms clean with a damp cloth or paper towel. Remove and set aside all stems; arrange the mushroom caps on a baking sheet with the gill-side up (stem side down).
• Finely chop about half of the reserved mushroom stems and set the chopped stems aside for the stuffing.
• Bake the mushroom caps on the baking sheet until they release some liquid, about 8–10 minutes. Remove the caps and transfer them to a layer of paper towels, placing them gill-side up (stem side down); gently blot any excess moisture.
• While the caps bake, finely chop the 1/2 medium onion, the 3 green onions, the 1 red bell pepper, and the 1/4 cup roasted red bell pepper (if the roasted pepper is not already chopped). Chop the 1/4 cup fresh parsley.
• Heat 2 tablespoons olive oil in a skillet over medium heat. Add the chopped mushroom stems, the chopped red bell pepper, the chopped roasted red bell pepper, the green onions, and the chopped onion. Sauté until the peppers and onions are tender, about 5 minutes. Stir in 1 teaspoon oregano, 1/2 teaspoon salt (or to taste), and 1/4 teaspoon pepper (or to taste).
• Transfer the cooked vegetable mixture to a bowl and let it cool slightly (a few minutes). Add the 1/4 cup parsley, 6 tablespoons breadcrumbs, and 4 tablespoons grated Parmesan cheese; mix until well combined.
• Return the mushroom caps to the baking sheet, gill-side up. Spoon the stuffing into each cap, pressing it in gently and mounding slightly.
• Bake the stuffed mushrooms at 400°F until the filling is heated through and lightly browned on top, about 15 minutes. Serve warm.