Preheat oven to 350°F (175°C).
In a bowl, combine melted butter, light brown sugar, granulated sugar, quick oats, salt, and all-purpose flour. Mix until crumbly.
In another bowl, toss together blueberries, lemon juice, granulated sugar, and cornstarch until well coated.
Spread the blueberry mixture evenly into a baking dish.
Sprinkle the crisp topping over the blueberries.
Bake in the preheated oven for about 45-50 minutes, or until the topping is golden brown and the blueberry mixture is bubbling.
Serve warm and enjoy!