Heat oven to 350ºF. Lightly spray cookie sheets with cooking spray. In large bowl, beat sugar, and vegetable oil spread with electric mixer until well blended. Add pumpkin, egg whites and orange peel; beat well. (Mixture will look curdled.) Add combined oats, flour, pumpkin pie spice, baking soda and salt; mix well. Stir in prunes and walnuts. Drop dough by rounded measuring tablespoonfuls about 2 inches apart on cookie sheets. Bake 11 to 13 minutes or until lightly browned. (Do not overbake; centers will be soft). Cool 1 minute on cookie sheets; remove to wire racks. Cool completely. For glaze, combine powdered sugar and orange juice in small bowl; mix well. Drizzle glaze over cooled cookies. Let stand until glaze sets. Store tightly covered.