8 cups pitted and diced fresh peaches (about 8 peaches)
1 tablespoon orange zest
2 tablespoons fresh orange juice
CRUST:
3 cups all-purpose flour
1 cup old-fashioned oats
1 cup firmly packed light brown sugar
1½ teaspoons baking powder
1 teaspoon kosher salt
1 cup cold unsalted butter, cubed
1 large egg
½ cup sour cream
1½ teaspoons vanilla extract
Instructions
Preheat oven to 350°. Line a 13x9-inch baking pan with foil; spray with baking spray with flour.
For Filling: In a large bowl, stir together brown sugar, cornstarch, cinnamon, ginger, and nutmeg. Add diced peaches and orange zest and juice, stirring until combined.
For Crust: In a large bowl, whisk together flour, oats, brown sugar, baking powder, and salt. Using a pastry blender or 2 forks, cut in butter until mixture is crumbly.
In a small bowl, whisk together egg, sour cream, and vanilla until smooth. Add egg mixture to flour mixture, stirring until combined. Dough will be crumbly. Using the bottom of a measuring cup, press three-fourths of dough into bottom of prepared pan. Bake for 10 minutes.
Spread peach filling evenly over crust. Sprinkle with remaining dough.
Bake until browned and set, 45 to 50 minutes. Remove from oven, and let cool completely. Refrigerate until set, about 2 hours or overnight.
Using foil as handles, remove from pan. Trim ½ inch off short edges and ¼ inch off long edges, and cut into 12 (3x2¾-inch) bars.