
Adjust oven rack to middle position and heat oven to 350 degrees. Grease 13 by 9-inch baking dish. Whisk condensed milk, flour, milk, and melted butter together in bowl. Pour batter into prepared baking dish. Sprinkle blueberries and sugar evenly over surface.
Bake until deep golden brown and toothpick inserted in center comes out clean, about 35 minutes. Transfer cobbler to wire rack; let cool for 10 minutes. Serve warm.