Pre-heat oven to gas mark 4/180°
Put margarine and sugar into the food processor and mix thoroughly. Add egg and mix again.
Add flour, baking powder, salt, oats, cranberries and nuts. Process again. Add chocolate and mix again.
Scrape all of the mixture from the processor and place in a bowl. Refrigerate mixture for 15 minutes.
Place tablespoons of mixture onto your prepared baking trays. Bake for 15 minutes - they may still look a little pale. Leave to cool and harden for 5 minutes before removing with a spatula.