Preheat the oven to 350°F (177°C). Line a 9-inch square baking pan with parchment paper, leaving enough overhang on the sides to lift out the baked bars.
Place the ripe bananas in a large mixing bowl and mash until mostly smooth.
Add the peanut butter, coconut or brown sugar, applesauce, and almond milk. Whisk until well combined.
Add the oats, baking powder, salt, cinnamon, and vanilla. Stir until everything is evenly incorporated.
Fold in the chocolate chips. The mixture should be thick but still easy to spread.
Transfer the mixture to the prepared pan and spread it evenly, smoothing the top.
Bake the Peanut Butter Banana Chocolate Chip Oatmeal Bars for 25–28 minutes, or until the center is set. The bars may still look slightly soft when they come out of the oven.
Cool in the pan at room temperature for 30–60 minutes.
Transfer the pan to the refrigerator and chill for approximately 1 hour. Chilling helps the bars firm up and makes them easier to slice cleanly.
Use the parchment overhang to lift the bars from the pan. Slice into individual portions and drizzle with melted peanut butter, if desired.