Step 1

Preheat your oven to 350ºF and grease an 8-inch square baking pan.

Step 2

In a large bowl, whisk together the oats, flour, brown sugar, baking soda and salt.

Step 3

Add the melted margarine and stir with a fork until evenly combined and large crumbs form.

Step 4

Reserve ½ cup of the crumb mixture for topping.

Step 5

Press the remaining mixture evenly and firmly into the bottom of your prepared pan.

Step 6

Bake for 12 minutes to set crust.

Step 7

While that is baking, combine the berries, sugar, cornstarch and lemon juice in a small saucepan, whisking until the starch dissolves.

Step 8

Heat over medium heat until the mixture comes to a simmer.

Step 9

Simmer, stirring occasionally, until the juices are no longer cloudy, about 2 minutes.

Step 10

Spoon the filling over the baked crust and evenly crumble the reserved crumb mixture over top.

Step 11

Bake for 30 minutes.

Step 12

Let cool completely in the pan, before cutting into squares.