Preheat the oven to 350°F. Line an 8x8 baking dish with parchment paper.
Add the rolled oats to a blender and blend until fine flour forms. Set aside.
In a large bowl, whisk the pumpkin puree, eggs, maple syrup, Greek yogurt, olive oil and vanilla until smooth.
Add the oat flour, protein powder, baking soda, ginger, salt and pumpkin pie spice. Stir until just combined.
Fold in the chocolate chips and walnuts.
Pour the batter into the lined dish and spread it evenly.
Bake for 45 minutes, until a toothpick in the center comes out clean.
Let cool, then lift out by the parchment and cut into 9 squares.