Preheat oven to 350°F.
Use a paring knife or apple corer to remove stems and seeds from the apples, making a deep hole where the filling will go.
Combine brown sugar, butter and cinnamon and rolled oats in a small bowl and mix well to combine. Add the nuts, raisins and rolled oats.
Spoon mixture evenly into each of the apples. Add 1/4 cup of water to a baking dish and place apples on top or you may also use individual ramekins.
Bake for about 40-45 minutes, or until apples are tender when pierced with a fork. Remove from oven and allow to cool for a few minutes. Spoon the sauce drippings from the pan over the apples. Serve with ice cream, if desired.