Preheat your oven to 350°F (175°C). Line a 9x13-inch baking pan with parchment paper, leaving an overhang for easy removal.

In a large mixing bowl, combine flour, rolled oats, granulated sugar, brown sugar, baking powder, and salt. Add the cold, cubed butter and use a pastry cutter or your hands to mix until crumbly.

Reserve 1 1/2 cups of the crumb mixture for the topping. Press the remaining mixture firmly into the bottom of the prepared pan to form the crust.

In a medium bowl, toss the sliced peaches with cornstarch and vanilla extract until evenly coated. Set aside.

In another bowl, beat the cream cheese, egg, and powdered sugar until smooth and creamy.

Spread the cream cheese mixture evenly over the crust in the pan.

Arrange the peaches on top of the cream cheese layer in an even layer.

Sprinkle the reserved crumb mixture evenly over the peaches.

Bake in the preheated oven for 40-45 minutes or until the top is golden brown and the filling is set.

Remove the pan from the oven and allow the bars to cool completely before slicing. For best results, chill in the refrigerator for at least 1 hour before serving.