Preheat the oven to 350°F (175°C). Grease a baking dish.

In a mixing bowl, combine rolled oats, flour, brown sugar, melted butter, salt, and cinnamon. Mix until crumbly.

Press half of the mixture into the bottom of the prepared baking dish to form the base.

In another bowl, combine blueberries, lemon zest, lemon juice, granulated sugar, and cornstarch. Toss gently to coat.

Spread the blueberry mixture evenly over the base in the baking dish.

Sprinkle the remaining oat mixture over the blueberry filling.

Bake in the preheated oven for 30 minutes or until the top is golden brown.

Allow to cool before cutting into bars.