Preheat your oven to 350°F (175°C). Prepare a 9x9 inch baking pan by greasing it lightly or lining it with parchment paper for effortless removal after baking.
In a large mixing bowl, combine the rolled oats, all-purpose flour, packed brown sugar, granulated sugar, salt, and baking powder. Mix well until the ingredients are evenly distributed.
Pour the melted unsalted butter and vanilla extract into the dry ingredients. Stir everything together until combined, resulting in a crumbly mixture resembling wet sand.
Reserve about two-thirds of this oat mixture, and press the remaining portion firmly and evenly into the bottom of the prepared baking pan, forming a solid base for your bars.
In a separate bowl, mix the sliced strawberries with cornstarch, lemon juice, and honey. Gently toss the strawberries to ensure they are evenly coated with the mixture, enhancing their flavor and thickening the juices.
Spread the strawberry mixture evenly over the pressed oat base in the baking pan, ensuring an even layer for a uniform taste.
Sprinkle the reserved oat mixture over the strawberries, creating a generous crumble topping that will bake into a golden crust.
Place the baking pan in the preheated oven and bake for about 30-35 minutes, or until the crumble topping is golden brown and the strawberry filling is bubbling joyously.
Once baked to perfection, remove the pan from the oven and let the bars cool in the pan for at least 15 minutes. This step ensures they set properly. Then, transfer the cooled bars to a wire rack to cool completely.
After cooling, cut the bars into squares and they're ready to be served!
Notes
Serve warm or at room temperature. Dust with powdered sugar for presentation.