preheat oven to 375. grease or spray a 2 quart casserole dish with either butter or cooking spray. in a medium bowl, toss together the oats, baking powder, cinnamon and salt.
in a separate bowl, whisk together the maple syrup, milk, egg, the melted butter and the vanilla.
place the diced apples in a single layer in the bottom of the prepared casserole dish.
sprinkle about two thirds of the raisins over the top of apples, then cover the fruit with the oat mixture. drizzle the milk mixture over the oats, making sure to distribute the milk as evenly as possible.
sprinkle the remaining raisins over the top of the oats. bake the oatmeal for 35-45 minutes until the top is golden brown and the oats have set.
remove the oatmeal from the oven and serve hot with more maple syrup.