Preheat oven to 350 degrees F. Lightly coat an 8x8 inch baking dish with cooking spray or line with parchment paper.
In a large bowl, stir together oats, baking powder, cinnamon, nutmeg, ginger, and salt.
In another medium bowl, whisk together milk, applesauce, maple syrup, eggs, and vanilla. Stir the milk mixture into the dry oat mixture until combined.
You can peel the apples if you want, or leave the skins on before dicing. Layer diced apples on the bottom of the baking dish and pour the oatmeal mixture over the apples. Spread evenly with a spatula. Sprinkle chopped pecans and brown sugar on top (if using)
Bake for 35-40 minutes or until the mixture is setup, golden brown and slightly crunchy on top. Remove from the oven and let it sit for a few minutes before slicing. Serve warm and enjoy!