Rub flour into margarine with fingertips until mixture resembles breadcrumbs. Mix in oats and sugar.
Halve dates, discarding stones. Core and finely chop apples. Toss chopped apple and dates together in shallow heatproof dish.
Spread over crumble topping. Bake at Gas Mark 5/375F/190 °C for 30-40 minutes until golden-brown.