Preheat your oven to 350°F (180°C).
Line an 8-inch square baking tin with foil, leaving a 2-inch overhang on all sides. Grease lightly.
In a large bowl, mix the flour, baking soda, salt, oats, and brown sugar.
Add the butter and cut it into the dry mixture until you have coarse crumbs that hold together when pressed.
Press two-thirds of this crumb mixture evenly into the base of the prepared pan.
Spread the jam in an even layer on top, leaving a ½-inch border on all sides.
Sprinkle the remaining crumb mixture over the jam, pressing gently.
Bake for 35 minutes, or until golden and bubbly.
Allow the bars to cool completely in the pan—about 1½ hours.
Lift out using the foil, peel it off, and cut into 16 squares.