1. preheat oven to 375 f (190 c)

2. slice each bell pepper in half lengthwise and remove seeds and membranes

3. lightly grease a baking dish and arrange pepper halves upright

4. heat olive oil in a skillet over medium heat

5. cook diced onion and minced garlic until fragrant, about 2 minutes

6. add ground chicken and cook until browned, breaking up meat as it cooks

7. stir in zucchini, spinach, crushed tomatoes, italian seasoning, and red pepper flakes and cook for 5 minutes

8. in a bowl, combine cooked quinoa, half of the mozzarella and parmesan cheese, and the chicken mixture, and season with salt and pepper

9. spoon the mixture into each pepper half and top with remaining cheese

10. cover dish with foil and bake for 20 minutes

11. remove foil and bake for an additional 10 minutes until cheese is bubbly and browned

12. let peppers cool for 5 minutes before serving