Preheat the oven to 180 °C (160 °fan/ 350 °F/ Gas 4).
Peel, core and slice the apples and place in a large pie dish (about 2 litres capacity).
750 g Granny Smith Apples
Mix in the blueberries, caster sugar, cinnamon and 1 tablespoon of flour.
300 g Blueberries, 1 tablespoon Caster Sugar, 1 teaspoon Cinnamon, 1 tablespoon Flour
In a mixing bowl place the plain flour, oats, and brown sugar and pour in the melted butter. Mix until a crumble topping forms.
125 g Plain Flour, 125 g Oats, 150 g Light Brown Sugar, 125 g Butter
Spoon the crumble topping over the fruit and bake in the oven for 45-50 minutes until the fruit is bubbling and the crumble topping is golden.