Preheat oven to 375°F.
Spray an 8-inch square baking dish with cooking spray.
In a large bowl, mix together the oats, baking powder, pumpkin pie spice, cinnamon and salt. Stir to combine.
Add in the milk, sweet potato, maple syrup, flaxseed, coconut oil and vanilla to the bowl. Stir well to combine.
Carefully pour oatmeal mixture into the prepared baking dish.
Mix together topping ingredients in a small bowl and sprinkle over oatmeal mixture.
Bake for 30 to 35 minutes, until the top is golden and center is set. Remove from the oven and let cool for a few minutes. Portion and serve.
Store in the refrigerator in an airtight container for up to 4 days.
To reheat the whole baked oatmeal, cover with foil and reheat in a 350°F oven for about 20 minutes. For individual portions, set toaster oven to 350°F and bake for 5-10 minutes or reheat in the microwave for 1 minute.