Preheat the oven to 190 C / Gas 5. Grease a small square baking tray and line with baking parchment.
Melt the margarine, syrup and sugar in a saucepan over a medium heat until completely melted. Pour the melted mixture into the flour and oats. Stir until it forms a thick dough. Fold in the chocolate chips or raisins. Transfer to the prepared baking tray and press evenly into the base with the back of a spoon.
Bake for 20 minutes until golden brown and firm. Remove from the oven and allow to cool for 20 to 30 minutes before removing from the tin. Cut into slices and then eat!