Preheat oven to 350°F (175°C).

Combine dry ingredients (flour, baking soda, baking powder, salt) in a bowl; set aside.

In a separate bowl, cut oleo (margarine) into sugar.

Add eggs, mashed bananas, and sour milk to the oleo and sugar mixture.

Mix well.

Gradually add the dry ingredients to the wet ingredients.

Mix until just combined; do not overmix.

Pour batter into a greased and floured loaf pan or cupcake liners.

Bake for 1 hour, or until a wooden skewer inserted into the center comes out clean.

If making cupcakes, bake for approximately 20-25 minutes.

Let cool in the pan for 10 minutes before transferring to a wire rack to cool completely.

Slice and serve.