Preheat the oven to 400 degrees F (200 degrees C). Grease a 9-inch square baking dish.

Whisk cornmeal, flour, sugar, baking powder, and salt together in a bowl. Beat milk, oil, and eggs together in a separate large bowl; stir in cornmeal mixture until just combined. Fold in blueberries; pour into the prepared baking dish.

Bake in the preheated oven until a toothpick inserted into center comes out clean, 25 to 30 minutes.