Preheat the oven to 350°F (175°C) and grease a 9x13-inch baking dish.
In a large bowl, whisk together the flour, baking powder, baking soda, salt, and sugar until well combined.
In another bowl, beat the eggs, then add the milk, melted butter, and vanilla extract. Mix until smooth.
Pour the wet ingredients into the dry ingredients and stir until just combined. Do not overmix; a few lumps are okay.
Gently fold in the blueberries.
Pour the batter into the prepared baking dish, spreading it evenly.
Bake in the preheated oven for 25-30 minutes, or until the top is golden brown and a toothpick inserted in the center comes out clean.
Allow the casserole to cool for 5-10 minutes before slicing. Serve warm with maple syrup drizzled on top.