01 -
Preheat oven to 350°F (175°C). Line an 8-inch square pan with aluminum foil and spray with cooking spray; set aside.
02 -
In a large microwave-safe bowl, melt the butter (about 1 minute on high power). Add flour, oats, sugars, and salt. Stir to combine until mixture is dry, sandy, and forms larger crumble pieces. Reserve 1 heaping cup for topping later.
03 -
Transfer the remaining mixture to the prepared pan. Use a spatula or your fingers to pack it down firmly, forming an even crust. Set aside.
04 -
In the same mixing bowl, add strawberries, sugar, lemon juice, and cornstarch. Toss to combine. Even if the sugar hasn’t dissolved fully, it will liquefy while baking.
05 -
Evenly spread the strawberry mixture over the crust. Sprinkle the reserved crumble topping over strawberries, pressing gently to form larger crumble pieces if desired.
06 -
Bake for about 50 minutes, or until the edges are set, the center is just set, and the crumble topping is lightly golden. If strawberries are very juicy, baking may take slightly longer.
07 -
Place the pan on a wire rack and allow to cool for at least 1 hour before slicing. Cutting before fully cooled may cause the bars to fall apart.