Preheat your oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper, leaving some overhang for easy removal.
Crust & Toppings
In a large bowl, combine the rolled oats, flour, brown sugar, granulated sugar, baking powder, salt, and ground cinnamon. Stir until well mixed.
Add the melted butter to the dry ingredients and mix until crumbly. Reserve 1 cup of this mixture for the topping.
Press the remaining oat mixture evenly into the bottom of the prepared baking pan to form the crust. Set aside.
Strawberry Filling
In a medium bowl, combine the chopped strawberries, lemon juice, granulated sugar, and cornstarch. Stir until the strawberries are well
Assemble the Bars
Spread the strawberry filling evenly over the crust in the baking pan.
Sprinkle the reserved oat mixture evenly over the strawberry filling.
Bake in the preheated oven for 35-40 minutes, or until the topping is golden brown and the filling is bubbly.
Allow the bars to cool completely in the pan on a wire rack. Once cool, use the parchment paper overhang to lift the bars out of the pan and onto a cutting board.