Pre heat your oven to 180C. To a large bowl add your cold cubed dairy free butter, caster sugar and gluten free plain flour. Using your fingertips rub the ingredients together until it starts to resemble breadcrumbs. Stir in the gluten free oats and set aside.
To a large large bowl or baking dish add the sliced apples and blackberries. Sprinkle over the caster sugar and mix well until everything is combined.
Sprinkle the crumble topping on top of the apple and blackberry mixture. Bake in the oven for around 40-45 or until golden brown and cooked through. Serve warm.