Preheat oven to 350 degrees. Grease and flour 9x5-inch loaf pan.
Whisk flour, sugar, 1 tablespoon lemon peel, baking powder, orange peel and salt in large bowl. Beat milk, oil, egg and vanilla in small bowl until well blended. Make well in flour mixture; pour in milk mixture and stir until well blended. (Batter will be thin.) Pour into prepared pan.
Bake 45 minutes or until toothpick inserted into center comes out clean. Cool bread in pan on wire rack 5 minutes.
Meanwhile, combine marmalade and remaining 1/2 teaspoon lemon peel in small microwavable bowl. Microwave on HIGH 15 seconds or until slightly melted. Remove bread from pan to wire rack; spread marmalade mixture evenly over top. Cool completely before serving.