These S'mores bars have all the ease of a classic bar, paired with more of everything you love in a classic campfire treat. They come together quickly and easily.
Arrange a rack in the middle of the oven and preheat oven to 350°F.
Coat a 9x13-inch baking pan with cooking spray and set aside.
Place the sugar and butter in a stand mixer fitted with the paddle attachment. (Alternatively, you can use an electric hand mixer and large bowl.) Beat on high speed until creamy and light in color, about 3 minutes. Add the egg and vanilla and beat on low speed until incorporated. While still on low speed, add the graham cracker crumbs, flour, baking powder and salt and beat until just combined.