Preheat the oven to 350°F (175°C). Line an 8x8-inch baking dish with parchment paper, letting the edges hang over for easy removal.

In a large bowl, mash the ripe bananas with a fork until mostly smooth.

Add honey or maple syrup, peanut butter, and vanilla. Stir until the mixture is glossy and combined.

Sprinkle in the rolled oats, cinnamon, and salt. Mix until every oat is moistened and the batter looks even.

Transfer the mixture to the prepared pan. Press it down firmly and evenly with the back of a spoon or your hand (wetting your fingers helps prevent sticking).

Bake for 20 to 25 minutes. The edges should turn golden brown and the center should be set but slightly springy.

Let the bars cool completely in the pan. Use the parchment overhang to lift them out, then slice into squares or rectangles.