Prepare a 9x9 baking pan by spraying with cooking spray. In a large bowl, combine rolled oats, brown sugar, cinnamon, baking powder, and salt.
In a separate bowl, combine milk, eggs, melted butter, and vanilla.
Next, pour the wet ingredients into the dry ingredients and mix until well incorporated. Gently, fold in the blueberries.
Pour the mixture into the prepared pan and spread out evenly.
Bake at 350°F oven for 30-35 minutes until the bars are cooked and the top is lightly browned. Allow the bars to cool, before slicing them into nine squares.
The Blueberry Oatmeal Bars can be stored in the fridge in an airtight container for 3-5 days; if they last that long.