01 -
Start heating your oven to 375°F (190°C). Line an 8-inch square pan with parchment, making sure there's enough extra for easy lifting when it's done.
02 -
Stir together the oats, brown sugar, flour, salt, baking soda, and cinnamon in a bowl. Add the melted butter and vanilla, mixing gently until it's crumbly.
03 -
With your crumb mixture, press half of it firmly and evenly into the pan you've prepared.
04 -
Mix the blueberries with cornstarch and granulated sugar until they're nicely coated. Spread them evenly across the pressed base.
05 -
Scatter the rest of the crumbly mixture over the blueberries and push it down lightly to keep it in place.
06 -
Bake it for 35-40 minutes, or until the top is golden and the blueberry layer is bubbly. Let it cool all the way before lifting it out using the parchment paper. Then cut it into squares.