Peel bananas and place in a medium bowl. Using a mixer with paddle attachment, mix bananas until smooth, then add butter and vanilla and mix until well combined. Add oatmeal, cinnamon, and cranberries, and mix until just combined. Spoon onto a baking sheet lined with parchment paper or a silpat then flatten with a fork. Bake at 350 for 20-25 minutes or until edges are golden.