Preheat your oven to 350°F (175°C).
In a mixing bowl, combine the mashed bananas, melted butter, beaten egg, and vanilla extract.
In another bowl, mix the rolled oats, flour, sugar, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, stirring until just combined.
Pour the batter into a greased loaf pan.
Bake for 50 minutes or until a toothpick inserted into the center comes out clean.
Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.