Preheat your oven to 350 degrees Fahrenheit. Grease an 8x8-inch baking pan with cooking spray or a light layer of butter so nothing sticks once it's baked. Set the pan aside while you get the batter ready.
In a large bowl, stir together the oats, baking powder, and salt until evenly combined. This little step keeps the baking powder from clumping in one spot, which helps the oatmeal rise evenly in the oven.
Add one cup of the chopped strawberries and the milk to a blender. Blend until smooth and pale pink. This strawberry milk is what gives the whole dish its fruity flavor, so don't skip it.
Pour the strawberry milk over the oat mixture, then add the melted butter, eggs, maple syrup, and vanilla extract. Stir until everything is fully combined, then fold in the remaining cup of chopped strawberries.
Pour the mixture into your prepared pan and spread it into an even layer. Arrange sliced strawberries across the top so every square gets a pretty berry topping once it's baked.
Bake for 35 to 40 minutes, until the top turns lightly golden and the center feels set. Let the pan cool for about 5 minutes before slicing into squares and serving warm.