The Bastyr Dining Commons often serves this popular dessert that can be made vegan and dairy-free by substituting the butter with soy margarine.
Preheat oven to 350 degrees Fahrenheit.
Mix blackberries, apples, sugars, tapioca, cinnamon and lemon juice, and spread evenly in a 9-by-13-inch baking pan.
In a clean bowl, mix oatmeal, 2 c. brown sugar and baking soda dry, then add melted butter. Cover fruit evenly with topping and bake until topping is brown, about 45 minutes.