I like to think of these fruit and oat bars as a grownup version of one of my favorite lunchbox snacks. I’ll bake these through spring and summer and bring them to picnics and cookouts every chance I get. The oat crumble comes together super quickly and the fruit layer works with just about any fresh or frozen berries that are on hand.
Preheat the oven to 375 degrees F. Spray a 9-inch square baking pan with baking spray and line with parchment paper, leaving an overhang on two sides of the pan (for easy removal after baking).
For the fruit: In a medium bowl, toss together the berries, sugar, lemon zest and juice, vanilla and salt. Set aside.
For the crumble: In a large bowl, combine the flour, oats, brown sugar and salt. Add the butter and use your hands to work the butter into the oat mixture until crumbly and combined.
Press a little more than half of the crumble into your prepared pan. Pour the sugared berries over the pressed crust and top with the remaining crumble.
Bake the bars for 25 minutes, then reduce the oven temperature to 350 degrees F and continue baking until the center is bubbly and the topping is golden, 30 to 35 minutes. Let cool completely, lift out of the pan and slice into 16 bars.