Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish.

In a large mixing bowl, combine all-purpose flour, granulated sugar, baking powder, and salt. Whisk until well blended.

Cut in the cold unsalted butter until the mixture resembles coarse crumbs, then stir in the egg.

Take half of the crumb mixture and press it into the bottom of the greased baking dish to form a crust.

In a separate bowl, mix sliced peaches, brown sugar, cornstarch, ground cinnamon, and nutmeg. Toss until peaches are coated.

Spread the peach mixture evenly over the crust in the baking dish.

Sprinkle the remaining crumb mixture over the peach layer evenly.

Bake for 45-50 minutes, or until the top is golden brown and the peach filling is bubbly.

Allow the bars to cool completely in the pan before slicing.

Cut into squares or rectangles and serve your delicious bars.