01 - Preheat the oven to 375°F. Lightly brush the bell peppers with olive oil and set aside.
02 - Cut the tops off the bell peppers and remove all seeds and membranes. Set aside.
03 - Heat 1 tablespoon olive oil in a large skillet over medium heat. Add onion and sauté for 2–3 minutes until softened. Add garlic and cook for an additional minute until fragrant.
04 - Add chopped spinach to the skillet and cook until wilted, about 2 minutes. Remove from heat.
05 - In a large mixing bowl, combine cooked chicken, spinach mixture, ricotta, 1/2 cup mozzarella, Parmesan, Italian herbs, salt, and pepper. Mix until evenly incorporated.
06 - Stuff each bell pepper evenly with the chicken Florentine mixture, pressing gently to fill completely.
07 - Arrange stuffed peppers upright in a baking dish. Spoon marinara sauce over each pepper and sprinkle with remaining mozzarella cheese.
08 - Pour about 1/4 cup water into the bottom of the baking dish to prevent sticking and help steam the peppers.
09 - Cover loosely with aluminum foil and bake for 25 minutes.
10 - Remove the foil and bake for another 10 minutes until the cheese is golden and peppers are tender. Let cool slightly before serving.