Combine first 4 ingredients in a medium bowl; make a well in center of mixture. Combine banana, milk, butter, egg, and vanilla; stir well. Add coconut; stir just until blended. Add banana mixture to dry ingredients, stirring just until dry ingredients are moistened.
Spoon batter into greased muffin pans, filling two-thirds full. Bake at 400° for 20 minutes or until muffins are golden. Let cool on a wire rack 5 minutes, and remove from pans.