Preheat your oven to 375°F (190°C).
Cut the tops off the bell peppers and remove the seeds and membranes. Set aside.
In a large skillet, heat olive oil over medium heat. Add onion and garlic, sauté until softened (about 3-4 minutes).
Add ground turkey to the skillet and cook until browned, breaking it up with a spatula as it cooks.
Stir in the diced tomatoes, cooked brown rice, oregano, basil, salt, and pepper. Cook for another 5 minutes until everything is well combined and heated through.
Place the bell peppers in a baking dish. Fill each pepper with the turkey mixture.
Cover the dish with foil and bake for 30-35 minutes.
Remove the foil, sprinkle mozzarella cheese on top of each pepper, and bake for an additional 5 minutes or until the cheese is melted and bubbly.
Garnish with fresh parsley before serving.