Preheat oven to 400°F.
Combine flour, sugar, baking powder and salt in a medium bowl.
Mix eggs, corn syrup, orange juice, oil and orange peel in a large bowl; stir in flour mixture just until moistened. Fold in berries and walnuts.
Spoon into 12 greased (2-1/2-inch) muffin cups.
Bake for 18 to 22 minutes or until lightly browned and firm to touch. Cool in pan 5 minutes; remove from pan. Serve warm.