Preheat the Oven:

Preheat your oven to 350°F (175°C). Grease a 9x9 inch baking dish or line it with parchment paper.

Mix Dry Ingredients:

In a large bowl, combine the oats, flour, brown sugar, salt, and baking powder.

Add Wet Ingredients:

Stir in the melted butter, beaten egg, and vanilla extract until the mixture is well combined.

Fold in Blueberries and Nuts:

Gently fold the blueberries and chopped nuts (if using) into the mixture.

Bake:

Spread the mixture evenly into the prepared baking dish. Bake for 25-30 minutes, or until the edges are golden brown and a toothpick inserted into the center comes out clean.

Cool and Slice:

Let the bars cool in the pan before slicing into squares.