Combine crumbs, 4 tsp. sugar and butter; press into bottom of 2-qt. oblong casserole or 8" spring-form pan, greased on bottom only. Bake in moderate oven (350°) 7 minutes. Cool. Line sides of spring-form pan with waxed paper.
Meanwhile, cover fruit with ½ c. sugar; let stand 1 hour. Then simmer in a heavy saucepan only until rhubarb loses crispness. Drain, reserv