Preheat oven to 350 degrees. Spray a 8×8 inch pan with non-stick cooking spray. Place all ingredients in the blender, except for the peanut butter, starting with the liquid ingredients first for easy blending. Blend until mix is smooth, and oats are ground. (Helpful Hint: You may need to stop the blender a few times and stir to mix things up at first!)
Pour mix into brownie pan, using a spatula to scrape the sides of the blender, and get all of the batter into the pan. (You don’t want to waste any, trust me!)
Microwave the peanut butter for 30 seconds. Drizzle the melted peanut butter over the brownie batter. Using a knife, gently swirl the batters together to make a marbled effect,. (Try not to overmix).
Bake for 20-25 minutes, or until brownies are cooked through. When brownies are completely cooled, cut brownies into 3 rows by 3 rows to get 9 even brownies.(I put them in the refrigerator to cool completely before cutting into them. They are very fudgy, so this helped them firm up a bit.)