Set your oven to 350°F and lightly coat a 9×13-inch baking dish with cooking spray. This prevents sticking and makes cleanup easier.

In a large mixing bowl, stir together the oats, brown sugar, baking powder, salt, and cinnamon to evenly distribute the dry ingredients. Then, add the eggs, milk, melted butter, and blueberries, stirring until fully combined. If using frozen berries, don’t thaw them first—this helps prevent them from turning the oatmeal purple.

Pour the oatmeal mixture into the prepared pan, spreading it evenly. Bake for 40 minutes, or until the center is set and the edges are lightly golden. If unsure, insert a toothpick—it should come out mostly clean.

Let it cool slightly before serving. Add a splash of milk, an extra sprinkle of sugar, or even a drizzle of maple syrup for a little extra sweetness. Leftovers? Store them in the fridge and reheat for an easy grab-and-go breakfast!