01 - Preheat the oven to 400°F. Lightly grease a baking dish.
02 - Using a sharp knife, cut a horizontal pocket into the side of each chicken breast, being careful not to cut all the way through.
03 - In a medium bowl, combine chopped spinach, crumbled feta cheese, minced garlic, fresh parsley, dill, lemon zest, and black pepper. Mix thoroughly.
04 - Divide the spinach-feta mixture evenly among the chicken breasts, spooning it into each pocket. Secure with toothpicks if needed.
05 - Rub the outside of each stuffed chicken breast with olive oil, salt, and pepper.
06 - Place the stuffed chicken breasts in the prepared baking dish. Drizzle with remaining olive oil and sprinkle with dried oregano.
07 - Bake for 25 to 30 minutes until the chicken reaches an internal temperature of 165°F and the top is lightly golden.
08 - Remove from the oven and carefully remove toothpicks before serving.