Preheat your oven to 375°F (190°C).
In a bowl, mix cream cheese, spinach, mozzarella, bell peppers, garlic, Italian seasoning, salt, and pepper.
Carefully slice each chicken breast horizontally to create a pocket.
Stuff each pocket with the cheese and vegetable mixture.
Secure the openings with toothpicks or kitchen twine.
Heat olive oil in a skillet over medium heat.
Sear the stuffed chicken breasts for 3-4 minutes on each side until golden brown.
Transfer the chicken to a baking dish and cover with foil.
Bake in the preheated oven for 20-25 minutes until cooked through.
Remove from the oven, let rest for 5 minutes, then serve.