In another bowl, whisk egg, then whisk in milk, applesauce, maple syrup, and vanilla. Pour into dry ingredients and mix well.
1 cup milk, 1 large egg, 1/2 cup unsweetened applesauce, 3 tablespoons maple syrup, 1 teaspoon pure vanilla extract
Slice peaches in half and discard pit. Cut peaches into slices or dice, whichever you prefer. (You do not need to peel the peaches.) Mix peaches into the oat mixture.
2 medium peaches
Pour mixture into prepared pan, smooth the top, and bake for 25-30 minutes, until firm and edges are brown.
Serve immediately with milk or maple syrup, or let cool completely to save for later. Store in the refrigerator and reheat individual squares in the microwave for about 45 seconds.