Mix together all-purpose flour, whole wheat flour, baking powder, baking soda, salt, and bran cereal. Stir in buttermilk, brown sugar, margarine, and egg until dry ingredients are fully combined. Add in dried fruit and walnuts.
Pour batter into a floured 9 x 5 inch loaf pan. Bake 1 hour or until a toothpick comes out clean. Flip bread out of pan and let cool.