Mix the 1 cup of bisquick and powdered sugar, cut in the margarine. Press in an ungreased 8" square pan. Bake in a preheated 350°F oven for 10 minutes until light brown. Mix all remaining ingredients and pour over slightly cooled baked layer. Return to oven and bake another 25 minutes more until set. Loosen edges while warm. Cool completely and spread with the glaze (beat together until smooth).