Preheat your oven to 350 degrees. Mist a 9x13 pan with cooking spray and set aside.
Mix your oats, brown sugar, baking powder, salt, cinnamon, eggs, 1 cup milk, melted butter, and blueberries if using in a large bowl. Pour into your prepared pan.
Bake 40 minutes or until set in the middle. Serve with additional sugar or milk as desired.
Notes
*We really like to use coconut milk in this recipe but you can use any variety.