In a small saucepan, combine rhubarb, sugar, and orange juice. Bring to boiling; reduce heat. Cover and simmer for 5 minutes or until rhubarb is tender.
Place berries in a blender or food processor bowl. Cover and blend or process until smooth. Add rhubarb mixture and lemon juice.
Turn into a 9x9x2-inch pan. Freeze at least 4 hours or until slushy. Scrape with a spoon into serving dishes or make parfaits, as suggested above. Makes 6 servings.