Pre-heat the oven at 190 C/Gas Mark 5
Peel, core and slice some dessert apples and put in the bottom of an oven proof dish.
Mix the flour, margarine and sugar until they are like breadcrumbs or, alternatively whizz the mixture for 15 seconds in the food processor. Stir in the oats and put the mixture on top of the apples.
Bake at 190 C/Gas Mark 5 for 40 to 45 minutes.