4 cups raspberries, divided
3/4 cup sugar
2 tablespoons cornstarch
1 cup flour
3/4 cup quick-cooking oats
1 cup packed brown sugar
1/2 cup cold margarine

Preheat oven to 350 degrees. Spray an 8-inch pan with cooking spray.

Crush one cup of berries and add enough water to bring level back up to one cup. Combine crushed berries, sugar and cornstarch in a small saucepan and bring to a boil. Cook and stir until thickened, approximately two minutes. Remove from heat. Stir in remaining 3 cups of raspberries and set aside to cool.

Combine flour, oats and brown sugar in a large bowl. Cut in margarine. Press half the crumbs into the bottom of the prepared pan. Spread with berry mixture and sprinkle with remaining crumbs. Bake for 45 minutes.