Preheat oven to 375 degrees and butter the inside of a 9 x 13-inch baking dish.
In a large bowl, mix together the oats, 1/4 cup of the almonds, baking powder, cinnamon, and salt.
In another bowl, whisk together the maple syrup, milk, egg, coconut oil or butter, and vanilla.
Sprinkle half of the apples over the bottom of the baking dish. Cover the fruit with the dry oat mixture. Slowly drizzle the milk mixture over the oats. Scatter the remaining apples and almonds over the top. Sprinkle with the brown sugar.
Bake for 40 minutes or until the oat mixture has set. Remove from the oven and let cool for a few minutes.
This may be eaten immediately or made ahead and reheated. Store leftovers in the refrigerator.