Heat oven to 400. Grease 12 muffin-pan cups. Whisk buttermilk, melted butter, egg and grated orange peel in medium bowl. Stir in berries. Combine flour, sugar, baking powder, baking soda and salt in large bowl. Add buttermilk mixture to dry ingredients, stirring just until moistened. Spoon into muffin cups. Bake 18 to 20 min. Serve warm.