Preheat oven to 350 degrees F and grease a 9x9 baking pan with nonstick cooking spray. Set aside.
Add oatmeal, baking powder, pumpkin pie spice, salt and brown sugar in a bowl and mix well. Stir in pumpkin puree, egg, milk and vanilla until mixed well.
Pour into prepared pan and spread evenly. Bake for 40-45 minutes until golden and the center is set. Remove from oven and cool for 5 minutes before slicing and serving.