A buttery oat crumb crust holds a thick layer of juicy cinnamon spiced peaches, with the same crumb mixture sprinkled back on top for a golden, craggy finish. This recipe skips fussy pie dough entirely—just press, fill, crumble, and bake for a peach dessert that's as easy as it is delicious.
Preheat oven to 375°F. Line a 9x13-inch pan with parchment paper with overhang on two sides, lightly spray with nonstick spray.
Whisk flour, oats, brown sugar, granulated sugar, baking powder, salt, and cinnamon in a large bowl. Cut in cold butter until pea-sized crumbs form. Stir in beaten egg and vanilla until shaggy crumbs form.
Set aside 1/3 of the crumb mixture for topping. Press the remaining 2/3 firmly into the prepared pan. Bake crust alone for 10 minutes until lightly golden and set.
Toss sliced peaches with sugar, cornstarch, lemon juice, cinnamon, nutmeg, vanilla, and salt in a large bowl. Let sit for 5-10 minutes, then stir again.
Spread peach filling evenly over par-baked crust, including all juices. Crumble reserved topping over the peaches; do not press down.
Bake for 35-40 minutes until topping is golden brown and filling bubbles at the edges. Tent with foil if browning too quickly.
Cool completely on a wire rack for 1 hour, then refrigerate for another hour to set the filling fully before slicing.
Whisk powdered sugar, milk, and vanilla for the glaze. Lift bars from pan using parchment sling, drizzle with glaze, and slice into 16 squares.
Notes
Use peaches that are ripe but still slightly firm to prevent a watery filling.
Chill the reserved crumb topping while the crust bakes so it stays cold and crumbly.
Do not skip the par-bake step—it keeps the crust from getting soggy.
Let the bars cool completely and chill before slicing for clean, neat squares.
Peel peaches for a smooth texture, or leave skins on for a more rustic bite.
For a mixed berry version, swap half the peaches for fresh blueberries or raspberries.
Add sliced almonds to the crumb topping for extra crunch.
Use frozen peaches straight from the freezer without thawing; add 5-10 minutes to the bake time.
Store bars in an airtight container in the refrigerator for up to 5 days or freeze for up to 3 months.
Warm individual bars in the microwave for 15 seconds if serving warm.