In a large mixing bowl, combine the oats, cinnamon, baking powder, and salt.
Create a well in the oat mix and add the milk, maple syrup, eggs, and vanilla. Whisk the eggs first and then mix all the ingredients together.
Place the blueberries on the bottom of the prepared baking dish and pour the oatmeal mix over blueberries. Gently stir the blueberries into oatmeal. Place the sliced blackberries on top of the oatmeal mix.
Bake for 35-40 minutes, or until edges and middle of oats have set.
Let cool slightly (you still want it warm) and top with some optional coconut whipped cream and/or pure maple syrup.
Leftovers will stay good in the fridge for 3-4 days and it's just as good reheated.
The estimated nutritional information is for the baked oatmeal only; it does not include the optional coconut whipped cream and/or pure maple syrup topping.