Preheat the oven: Set the oven to 350°F (175°C). Grease or line an 8×8-inch baking pan with parchment paper.

Mix the dry ingredients: In a large bowl, combine rolled oats, baking powder, cinnamon, nutmeg, and salt. Whisk until evenly mixed.

Mix the wet ingredients: In another bowl, whisk together the egg, milk, maple syrup, vanilla extract, and applesauce until smooth.

Combine: Pour the wet ingredients into the dry mixture and stir gently until fully incorporated.

Add the fruit and nuts: Fold in the chopped apples and nuts (if using), ensuring they’re evenly distributed throughout the batter.

Bake: Transfer the batter to the prepared pan and spread it evenly with a spatula. Bake for 35–40 minutes, or until the top is golden brown and a toothpick inserted in the center comes out clean or with moist crumbs.

Cool and serve: Let the baked oats cool in the pan for at least 15 minutes before slicing into bars or squares. Serve warm or at room temperature.