Preheat the oven to 400 degrees F. In a large mixing bowl stir together the flour, oatmeal, brown sugar, baking powder, cinnamon, and salt. Set aside. Lightly coat muffin pan with cooking spray or grease with shortening.
In a blender container combine milk, egg, and oil. Cover and blend smooth.
With blender running, add banana and blend into mixture. Pour into dry ingredients and stir just until moistened. Fill muffin pans 2/3 full. Bake in the 400 degree F oven about 20 minutes or until a wooden toothpick inserted in center comes out clean. Makes 10 to 12.