Peel and slice apples into slices or cubes and place in the bottom of a baking dish.
In a food processor add all remaining ingredients and pulse until combined. If making by hand, using your fingers, a pastry cutter or 2 forks, add the butter, flour and rolled oats to a medium sized bowl and rub it together until the butter is combined and there are only small pieces left. Add the rest of the crumble ingredients and combine.
Pour the crumble topping over the apples and bake for 30-40 minutes until the apples are cooked and the crumble is golden.
Remove from the oven and serve immediately with yoghurt or vanilla ice-cream.
Store covered in the fridge for up to 5 days, reheating portions in the microwave.