Preheat the oven to 350 degrees. Spray a 8×8 inch pan with non-stick spray and set aside.
Put all of the ingredients, except for the peanut butter, into a blender. Putting the liquid ingredients into the blender first makes blending easier. Blend until the mixture is smooth and oats are ground up.
Pour batter into prepared baking dish.
Microwave peanut butter for about 30 seconds. Drop melted peanut butter by spoonfuls onto the batter, swirling gently with a knife to create a marbled effect. If you overmix, you'll loose the marbling effect.
Bake for 20-25 minutes or until brownies begin to pull away from the sides of the pan (mine took a little longer - more like 30 minutes).