Core the apples, making sure to leave the bottom intact for stuffing.
In a mixing bowl, combine the rolled oats, brown sugar, cinnamon, chopped walnuts, raisins, melted butter, and a pinch of salt. Mix everything together until well combined.
Spoon the filling mixture into each apple, packing it tightly.
Place the stuffed apples upright in a baking dish. Pour apple juice or water into the bottom of the dish to create steam while baking.
Cover the baking dish with aluminum foil and bake in the preheated oven for 25 minutes. Then, remove the foil and bake for an additional 15-20 minutes until the apples are tender and the filling is golden.
Once baked, let the apples cool slightly before serving.
Notes
Serve warm with vanilla ice cream or whipped cream.