Combine cake mix and coconut; cut in butter till mixture resembles coarse crumbs.
Lightly press into bottom and 1/2 inch up sides of 13x9x2-inch baking pan.
Bake in 350° oven for 10 to 15 minutes.
Arrange peaches over crust.
Combine sugar and cinnamon; sprinkle evenly over peaches.
Blend sour cream and egg; pour over all.
Bake in 350° oven just till sour cream is set, about 10 minutes.