Preheat oven to 350 degrees and prepare a 9-inch round baking dish by spraying with nonstick cooking spray.
In a large bowl, combine the pumpkin puree, brown sugar, eggs, pumpkin pie spice, baking powder, cinnamon, vanilla extract and salt. Whisk to mix.
Add the milk and whisk until combined.
Stir in the oats and set bowl aside.
To make the streusel topping, combine apples, flour, brown sugar, salt, and cinnamon in a medium mixing bowl. Stir to mix. Pour the melted butter into the bowl and stir to combine.
Pour the oat mixture into the prepared baking dish and spread it evenly.
Top the oatmeal mixture with the streusel mixture.
8. Bake uncovered for 45 minutes. Allow to rest for 5 minutes before serving.
