Prep the pan and oven: Heat the oven to 350°F (175°C).
Grease an 8x8-inch baking pan or line it with parchment for easy removal.
Mix the wet ingredients: In a large bowl, whisk milk, applesauce or banana, maple syrup, eggs, melted butter, and vanilla until smooth.
Add the dry ingredients: Stir in oats, cinnamon, baking powder, and salt. Fold gently until combined. The mixture will look a bit loose—this is good.
Stir in add-ins: Fold in fruit or other add-ins.
If using grated zucchini or apple, squeeze out extra moisture with a clean towel first.
Rest briefly: Let the mixture sit for 5 minutes so the oats start to absorb liquid. This helps it hold together after baking.
Fill the pan: Pour the mixture into the prepared pan and spread it into an even layer.
Bake: Bake for 28–35 minutes, until the edges are set and the center is just firm to the touch. A toothpick should come out mostly clean.
Cool and slice: Let it cool in the pan for at least 10 minutes.
Slice into small squares or bars for toddlers. Serve warm or at room temperature.
Serve: Add a drizzle of yogurt, a splash of milk, or a smear of nut butter on top for extra creaminess and protein.