Heat oven to 400°F. In large bowl, combine berries, sugar and cornstarch; toss gently. Spoon evenly into ungreased 8-inch square (1 1/2-quart) baking dish.
In small bowl, combine flour, oats, brown sugar, cinnamon and margarine; mix until crumbly. Sprinkle over fruit.
Bake at 400°F. for 25 to 30 minutes or until edges are lightly browned and fruit mixture is bubbly. Cool slightly. Serve warm or at room temperature. If desired, top with nonfat vanilla ice cream.