- Preheat oven to 375°F. Line a large rimmed baking sheet with foil and mist with cooking spray.
- Using a spoon, carefully remove mushroom gills and discard. Place mushrooms on prepared sheet, cap side down, and brush with 1 tbsp oil.
- In a medium skillet on medium-high, heat remaining 1 tbsp oil. Add garlic and cook, stirring constantly, until fragrant, about 30 seconds. Add zucchini and cook, stirring frequently until golden, about 3 to 4 minutes. Add spinach and cook, stirring frequently, until wilted, about 1 minute more. Place spinach mixture on top of each mushroom, dividing evenly. Sprinkle each mushroom with 1 tbsp bread crumbs. Top with red peppers and tomatoes, dividing evenly.
- Prepare sauce: In a small saucepan, melt butter over medium heat until foamy. Add flour and stir constantly for 30 to 45 seconds. Slowly add milk, stirring constantly and cook until slightly thickened, about 1 minute. Remove from heat and stir in cheese until melted.
- Divide sauce evenly between mushrooms and bake until mushrooms are softened and sauce is golden, about 15 minutes. Garnish with thyme (if using).
- Serving Size 1 stuffed mushroom
- Calories 144
- Carbohydrate Content 13.5 g
- Cholesterol Content 8 mg
- Fat Content 9 g
- Fiber Content 4 g
- Protein Content 5 g
- Saturated Fat Content 3 g
- Sodium Content 99 mg
- Sugar Content 5 g
- Monounsaturated Fat Content 0 g
- Polyunsaturated Fat Content 1 g