Preheat the oven to 375 degrees F. Line an 8x8-inch pan with parchment paper so it overhangs on two sides so the bars are easy to lift out once baked and cooled.
Mix together all of the ingredients in a medium bowl except the blueberries. Stir in the blueberries gently.
Press into the prepared pan so the batter is even and pressed to the edges.
Bake for 24-26 minutes or until the edges are lightly golden brown and set.
Cool fully. (Really, please let it sit until it is cool to the touch! You can pop it into the fridge to speed this up if you'd like. It may crumble a bit if you slice when still warm.)
Slice into bars and serve or store. I typically cut into 16 small squares, but you can cut them larger if desired.
