Combine in a medium bowl the egg, orange rind, juice, milk, melted butter and oatmeal. Let the mixture soak while you do the next step.
Combine in a larger bowl the flours, baking powder and soda, sugar, salt, and cranberries, plus walnuts if you are using them.
Quickly and briefly stir the liquid ingredients into the dry ingredients, just until combined. Fill 12 paper lined muffin cups with the batter. Bake at 400 degrees until the muffins bounce back when tapped on the top, about 18 minutes.