Combine mixed berries, dried cranberries, cranberry juice, tapioca, cinnamon, and sugar in bottom of a 4 or 5-quart slow cooker. Stir thoroughly.
Cover and cook on high setting for 2 to 4 hours.
For crumble topping:
Preheat oven to 350 degrees F, 30 minutes before serving, Line a baking sheet with aluminum foil and set aside.
In a medium bowl, combine crumble topping ingredients. Spread out on prepared baking sheet and bake for 12 to 18 minutes or until crisp and golden brown.
Sprinkle crumble topping over warm berry mixture.
Serve with vanilla ice cream or with whipped topping, if desired.