Preheat oven to 350° F. Coat sides and bottom of 9×13 inch baking pan with cooking spray or wipe with coconut oil.
Combine oats, flour, and brown sugar in a mixing bowl. Whisk to combine. Add the cubed butter and squeeze into the dry ingredients using your hands until a coarse breadcrumb-like texture is achieved and ingredients are combined thoroughly. Transfer mixture into the 9×13 inch pan and press down. Place in oven and bake for 12 minutes.
In the meantime, bring milk to a boil with the cinnamon, nutmeg, and salt. As soon as it boils, transfer to a large mixing bowl. Stir in the pumpkin first and then add the protein powder and eggs. Next add Splenda to sweeten, if necessary. Once the crust has finished baking, remove from the oven and pour the pumpkin filling on top. Place back in the oven and bake for 20-25 minutes or until pumpkin filling has set (should be firm to the touch in the center). Allow to cool before serving and store in the refrigerator.
