Preheat your oven to 375°F (190°C). Line an 8×8-inch baking pan with parchment paper, leaving an overhang for easy lifting.
In a large mixing bowl, mash the bananas until mostly smooth.
Stir in the Greek yogurt, peanut butter, and vanilla extract until fully combined.
Add the rolled oats and chocolate chips. Mix until a thick batter forms.
Spread the Banana Oatmeal Bars mixture evenly into the prepared baking pan. Press firmly with the back of a spoon to create an even layer.
Sprinkle additional chocolate chips over the top if desired.
Bake for 12–15 minutes, or until the center is just set. Avoid overbaking to keep the bars soft and moist.
Let cool completely before lifting from the pan.
Slice into squares and serve.