Heat the oven to 350F.
In a large bowl, combine the first 13 ingredients (through pumpkin). Whisk in the flour, baking powder, baking soda, and protein powder. Spread in a 13x9 baking dish sprayed with cooking spray.
In a small bowl, combine the walnuts and oats. Sprinkle the walnut-oat mixture over top of the brownie batter.
Bake at 350F for 35 minutes or until set (be sure to check for doneness in the center! - this batter can trick you and look set, but then be raw in the center when you cut it). Yield: 24 bars.