Preheat the oven to 350F and grease an 8X8 glass baking dish.
In a medium bowl, combine the oats, sugar, brown sugar, baking powder, cinnamon, and salt. Mix well.
Add in the milk, eggs, and vanilla extract. Whisk until well combined.
Whisk in the melted butter.
Fold in the chopped and peeled apple.
Pour the oatmeal mixture into the prepared baking dish and bake in the oven for 40-45 minutes.
Allow to cool for 5-10 minutes before slicing and serving with milk or whipped cream.