1. Preheat oven to 375°F (190°C).
2. Make a deep cut along the side of each chicken breast to create a pocket. Be careful not to cut all the way through.
3. Stuff each chicken breast with equal amounts of roasted red peppers, spinach, and mozzarella cheese.
4. Secure the opening with toothpicks if necessary.
5. In a small bowl, mix together the olive oil, garlic powder, Italian seasoning, salt, and pepper. Brush this mixture over both sides of the chicken breasts.
6. Place the stuffed chicken breasts in a baking dish and bake for 25-30 minutes, or until the chicken is cooked through and no longer pink inside.