Preheat the grill over medium high heat (approximately 350 degrees Fahrenheit).
Cut the bananas in half lengthwise with the peels still on.
Brush each half of the banana with the melted butter on the cut side.
In a small mixing bowl, whisk together the brown sugar and ground cinnamon.
Place the cut side of each banana with the cinnamon and sugar mixture.
Brush the grill grates with the olive oil to keep the bananas from sticking.
Place the bananas, cut side down, on the grill and cook for 2-3 minutes.
Flip the bananas, peel side down, and grill for 3-4 more minutes until browned and the banana starts to pull away from the peel.
Remove from the grill. Serve as is or remove the peels from the bananas and serve warm. Enjoy!