Add the rolled oats, milk, and peanut butter into a clean jar or container with a lid.
Stir the mixture thoroughly with a fork or spoon until the peanut butter is fully blended into the oats and liquid, creating a smooth, uniform base.
Slice the ripe banana into thin rounds and layer them on top of the oat mixture, pressing them slightly into the surface.
Seal the jar or container tightly with the lid and place it in the refrigerator overnight, allowing the oats to soak and thicken.
In the morning, remove the jar from the fridge and give it a gentle stir to combine the layers and redistribute the flavors.
Taste the oats and top with additional banana slices, a drizzle of honey, or a sprinkle of cinnamon if desired before serving.
