Step 1

Preheat the oven to 375°F (190°C). Line an 8-inch square baking pan with parchment paper, leaving some overhang for easy removal.

Step 2

In a large bowl, mix together oats, flour, brown sugar, baking soda, salt, and cinnamon (if using).

Step 3

Stir in melted butter and vanilla extract until the mixture is crumbly.

Step 4

Press half of the oat mixture firmly into the bottom of the prepared pan to form a base.

Step 5

In a separate bowl, toss blueberries with granulated sugar and cornstarch. Spread the blueberry mixture evenly over the oat base.

Step 6

Crumble the remaining oat mixture over the blueberries, gently pressing down.

Step 7

Bake for 35-40 minutes, or until the top is golden brown and the blueberries are bubbly.

Step 8

Allow the bars to cool completely in the pan on a wire rack. Once cooled, use the parchment paper overhang to lift the bars out of the pan and cut into squares.