Preheat your oven to 180°C (350°F) and line an 8×8-inch baking pan with parchment paper.
In a large bowl, combine the flour, granulated sugar, brown sugar, baking powder, and salt.
Add the softened butter, egg, and vanilla extract. Mix until a crumbly dough forms.
Press two-thirds of the dough firmly into the prepared baking pan to create the crust.
In another bowl, stir together the peaches, sugar, cornstarch, lemon juice, and cinnamon until evenly coated.
Spread the peach mixture evenly over the crust.
Sprinkle the remaining crumb mixture over the peaches.
Bake the Peach Crumb Bars for 35–40 minutes, or until the top is lightly golden and the filling is bubbling.
Allow the bars to cool completely before slicing into squares.
Serve and enjoy.