Line a 9x13 inch baking dish with parchment or wax paper, leaving an overhang over the edges. Set aside.
In a large bowl, stir together the oats, coconut and cocoa powder until well combined. In a small bowl, whisk together the mashed banana, melted coconut oil, honey, brown sugar, vanilla and salt until smooth and well combined. Pour this wet mixture into the dry ingredients and stir until everything is evenly combined and no dry bits remain.
Pour this mixture into the prepared baking dish, and press it down firmly with damp hands. Place another piece of wax paper over top of the bars in the pan, and use the back of a metal flipper to press down on the bars again, compressing them as much as possible. This will keep them from being crumbly.
Place the pan of bars in the refrigerator. Allow them to chill for at least one hour before lifting them out of the pan and slicing into bars. Store in the fridge in an airtight container for up to one week.