Preheat the oven to 3750F (1900C).
In a mixing bowl, combine the chopped spinach, feta cheese, sun-dried tomatoes, minced garlic, salt, and pepper.
Using a sharp knife, make a pocket in each chicken breast by cutting a slit lengthwise, being careful not to cut through the other side.
Stuff each chicken breast with the spinach and feta mixture.
In a large skillet, heat olive oil over medium-high heat. Add the stuffed chicken breasts and cook for 5-7 minutes on each side or until golden brown.
Transfer the skillet to the preheated oven and bake for 15-20 minutes or until the chicken is cooked through.
Serve hot with your favorite side dish.
