Preheat and prep: Heat your oven to 350°F (175°C).
Line an 8x8-inch baking pan with parchment paper or lightly grease it to prevent sticking.
Mash the bananas: In a large bowl, mash the ripe bananas with a fork until mostly smooth. A few small lumps are fine.
Add wet ingredients: Stir in 1/3 cup unsweetened applesauce (or yogurt), 1 beaten egg, and 1 teaspoon vanilla extract if using. Mix until combined.
Stir in dry ingredients: Add 2 cups rolled oats, 1 teaspoon baking powder, 1/2 teaspoon cinnamon, and a tiny pinch of salt.
Stir until everything is evenly moistened. The mixture will be thick and spoonable.
Customize (optional): Fold in 1–2 tablespoons ground flaxseed or chia seeds, or 1/2 cup soft berries. Keep pieces small for toddler safety.
Avoid hard nuts for very young children.
Spread and smooth: Transfer the mixture to the pan and press it into an even layer. A spatula or the back of a spoon works well.
Bake: Bake for 18–24 minutes, until the edges are set and lightly golden and the center feels firm to the touch. A toothpick should come out with just a few moist crumbs.
Cool completely: Let the pan cool on a rack for at least 20 minutes.
This helps the bars set and slice cleanly.
Slice and serve: Lift the bars out using the parchment and cut into small squares or finger-sized bars. Serve plain or with a thin spread of nut butter for older toddlers if safe.