- Clean mushrooms with a damp paper towel, remove stem and set aside. Remove dark gills by running a teaspoon under the gills; scrape and discard. Brush mushroom generously with olive oil on the inside and outside; set aside until stuffing is ready.
- Sauté onion and celery in 2 tablespoons of olive oil in a skillet over medium heat until vegetables are softened and beginning to brown, about 10 minutes. Add garlic and continue to cook 3-4 minutes or until garlic is fragrant. Transfer onion, celery, and garlic from the skillet to a medium sized mixing bowl.
- Add zucchini and red pepper to the same skillet with 2 tablespoons olive oil and cook over medium heat until vegetables soften and release extra moisture, about 5 minutes. Sprinkle with Italian seasoning, salt, and pepper and cook for 2-3 more minutes to meld flavors. Transfer to the mixing bowl with the onions and celery, stir to combine. Allow mixture to cool slightly while grill is preheating.
- Just before grilling, toss blue cheese into vegetable stuffing then salt and pepper, to taste. Spoon evenly into the mushrooms. Top with additional blue cheese and grill over medium-low heat or in a preheated 350° oven for 8-10 minutes. Mushrooms will soften and wilt slightly when done. Use a spatula to remove from the grill and serve immediately or transfer to an oven safe dish to keep warm in a 200° oven until ready to serve.
You can add crumbled, browned sausage to make this more of a main course
This recipe can also be made using 12 or more baby portabella mushrooms and serving as an appetizer. To save time on the day of your party, make the stuffing in advance and vacuum package/freeze it. Thaw on the day of the event and stuff your mushrooms.