Preheat the oven to 350°F. Line an 8-inch square baking pan with parchment paper, leaving enough paper hanging over the sides to lift out the bars.
Mix the oats, oat flour, vanilla protein powder, brown sugar, cinnamon, salt, and melted butter until the mixture resembles damp crumbs.
Press two-thirds of the oat mixture firmly into the bottom of the prepared pan. Bake for 10 minutes, then let the crust cool slightly.
Blend the cottage cheese, Greek yogurt, eggs, maple syrup, cornstarch, and vanilla until smooth and creamy.
Toss the peaches with the lemon juice and brown sugar. Arrange the peaches over the warm crust.
Pour the cottage cheese filling over the peaches and sprinkle the remaining oat mixture evenly over the top.
Bake for 38 to 45 minutes, until the center is nearly set and the topping is golden brown.
Cool the bars completely, then refrigerate for at least 3 hours before slicing.