Mix together milk, lemon juice and thawed Cool Whip. Fold in pineapple and orange sections. Pour into crusts. Refrigerate until firm or freeze. Thaw in refrigerator.
VARIATION: CRANBERRY-ORANGE PIE: Substitute 1 can whole berry cranberry sauce for pineapple. Use 1 large can mandarin oranges or 2 (11 oz.) cans.