In a large bowl, combine the cracker crumbs, sugar and butter; press into an ungreased 13-in. x 9-in. baking pan. Bake at 350° for 10 minutes. Combine coconut and milk; spread over crust. Bake 15 minutes longer.
In a microwave, melt chocolate chips and peanut butter; stir until smooth. Spread over top. Cool completely on a wire rack before cutting.