Preheat the oven to 180°C. Grease and line a medium size loaf tin.
Cream the margarine and sugar together, then add the eggs and vanilla and mix until fluffy.
Mix the flour, oats, baking powder, bicarbonate of soda and cinnamon together. Add this mixture to the egg mixture.
Mash the bananas with the milk, then gently combine with the batter. Fold in the raisins, if used, then spoon the batter into the tin.
Bake for 50 to 60 minutes, until the top is golden and an inserted skewer comes out clean. Let it cool for 5 minutes in the tin, then transfer to a wire rack to cool completely.