Combine the flour, oats, brown sugar, cocoa, baking powder and baking soda in a large bowl. In a medium bowl, combine the mashed bananas, soymilk, margarine and vanilla. Add the banana mixture to the dry ingredients and stir until just moistened.

Spoon the batter into prepared muffin cups and bake for 20 to 25 minutes until a toothpick inserted into the centre of the muffins comes out clean. Cool on a wire rack.