1 and 1/2 cups all-purpose flour
3/4 cup light-brown sugar
1/2 cup (1 stick) cold unsalted butter, cut into small pieces
1 teaspoon salt
5 pints blackberries
2 tablespoons instant tapioca
3/4 cup granulated sugar
1 tablespoon grated orange zest, plus 1/4 cup fresh orange juice
Preheat oven to 375 degrees. In a food processor, pulse flour, brown sugar, butter, and salt until combined.
In a large bowl, toss together blackberries, tapioca, granulated sugar, and orange zest and juice.
Pour blackberry mixture into a 2-quart baking dish.
Sprinkle evenly with flour mixture.
Bake until top is golden and juices are bubbling, 50 minutes.
Let cool 20 minutes.
Serve warm with vanilla ice cream.