Thaw berries until most of free ice has disappeared. Drain off juice, measure and add water to make ½ c. liquid; stir into mixture of sugar, tapioca and cornstarch in saucepan. Heat rapidly until thickening is complete. Boiling is not necessary. Set aside to cool.
Add berries and lemon juice to cooled, thickened juice. Pour filling into pastry-lined 9" pie pan. Cut steam vents and adjust top crust; flute edges.
Bake in hot oven (425°F.)30 minutes, or until nicely browned. For a brown undercrust, bake on lowest oven shelf.