Pre-heat oven to 160° C/140° C (fan-forced) and brush a 21.5 x 11.5 x 5.5cm loaf tin with margarine spread and line with baking paper.

Using a microwave oven or stove top, melt margarine spread and cool.

Place cooled margarine spread, brown sugar, vanilla extract and eggs in mixing bowl. Mix with a wooden spoon until well combined.

In a small bowl, mix the bicarbonate of soda into the buttermilk and add to the liquid ingredients with the flours, oats and banana. Mix until well combined.

Pour mixture into the prepared tin and sprinkle with the topping mixture.

Bake for 40-45 minutes or until golden and when a skewer inserted in the centre comes out clean.

Cool for a few minutes in the tin before transferring to a wire cooling rack, removing the baking paper and cooling completely.

Serve cut into slices.

Make topping by mixing the oats, margarine spread, brown sugar and cinnamon together with a wooden spoon until well combined. Set aside