Preheat your oven to 375°F and line a 9x13 inch baking dish with parchment paper, leaving some overhang on the sides for easy removal later. In a medium bowl, combine the oats, flour, brown sugar, ground ginger, and kosher salt. Pour in the melted butter and vanilla extract, stirring until the mixture is evenly moistened and crumbly. Press about 3/4 of this mixture firmly into the prepared pan to create an even base layer—I like to use the bottom of a measuring cup to pack it down smoothly, which helps it hold together better when baking.

While the crust base is ready, prepare your filling by tossing the chopped strawberries with cornstarch, lemon juice, lemon zest, and granulated sugar in a separate bowl—let this sit for a minute so the cornstarch can start absorbing the berry juices. Spread half of the strawberry mixture evenly over the oat crust, then top with the remaining strawberry mixture. This two-layer approach helps distribute the filling more evenly throughout the bars. I find that the cornstarch thickens the berry juices just enough to prevent the crust from getting too soggy while still keeping the fruit flavor bright.

Sprinkle the reserved 1/2 cup of oat mixture over the strawberry filling, distributing it as evenly as possible without pressing down—this creates a nice textured topping that will stay crispy. Bake at 375°F for 35–40 minutes, until the oat topping is golden brown and the filling is bubbling slightly at the edges. The bars are done when the top is set but still has a bit of give when you gently press it.

Remove the bars from the oven and let them cool completely on the countertop—this typically takes 30–45 minutes. While they cool, whisk together the sifted icing sugar, vanilla extract, and whole milk in a small bowl until smooth and pourable. Once the bars are completely cool, use the parchment paper overhang to lift them out of the pan and transfer to a cutting board. Drizzle or spread the glaze evenly over the top, then cut into 12–16 bars with a sharp knife (wiping the blade between cuts keeps the edges clean).