Preheat oven to 350 degrees F. Line an 8x8 inch square baking pan with parchment paper. Add all of the dry ingredients including the rolled oats, oat flour, baking powder, pumpkin pie spice, cinnamon, and salt to a large bowl and mix together.
In another medium-sized bowl, beat the egg and add the pumpkin puree, mashed banana, maple syrup, and vanilla extract. Stir to combine.
Add the wet ingredients to the dry ingredients and mix until well combined. Fold in the chocolate chips, if using.
Evenly distribute the mixture into a square parchment paper lined baking pan. Poke a few extra chocolate chips into the surface of the bars.
Bake for 20-25 minutes or until an inserted toothpick comes out clean. Allow them to cool for at least 15 minutes.
Use the parchment paper as a sling to remove the baked oatmeal mixture from the pan. Slice into 12-16 bars. Store in an airtight container in the fridge for up to four days or the freezer for up to three months.