Preheat oven to 350°F (175°C) and spray a baking dish with nonstick cooking spray.
Core each apple, ensuring not to cut through the bottom.
In a bowl, combine granola, brown sugar, cinnamon, and melted butter until crumbly.
Generously stuff each apple with the mixture and place them upright in the baking dish.
Add a splash of water to the bottom of the dish, cover loosely with foil, and bake for 25 minutes. Remove foil and bake for an additional 10-15 minutes until tender.
Allow to cool slightly before serving warm.