Preheat your oven to 350°F. Line an 8x8 inch baking pan with parchment paper or spray with cooking spray and set aside.
Put 2 cups of the quick oats in a blender or food processor and blend until you’ve created oat flour.
Transfer the oat flour to a large mixing bowl. Add the remaining oats, pumpkin pie spice, baking powder and salt and stir to combine.
Add pumpkin, maple syrup, coconut oil, flaxseed and vanilla to the dry ingredients and mix well until combined.
Gently fold in the chocolate chips and walnuts.
Pour the batter into the prepared baking dish. Scatter additional chocolate chips and walnuts on top, gently pressing them down.
Bake for about 20-25 minutes, until the bars are cooked through and a toothpick insured comes out clean.
Allow the bars to cool completely in the pan before cutting into 9 bars and serving.