Preheat your oven to 350°F (175°C) and grease a 9x9-inch baking pan or line it with parchment paper for easy removal.
In a large mixing bowl, combine the rolled oats, flour, brown sugar, baking soda, and salt. Mix well.
Pour the melted butter and vanilla extract into the dry ingredients and stir until everything is well combined and crumbly.
Press half of the oat mixture firmly into the bottom of the prepared baking pan to form a crust.
Spread the raspberry jam evenly over the crust. If using fresh raspberries, scatter them evenly over the crust instead.
Sprinkle the remaining oat mixture over the top of the raspberry layer, pressing it down gently.
Bake in the preheated oven for 25-30 minutes, or until the top is golden brown.
Allow the bars to cool in the pan for at least 15 minutes before cutting into squares. For best results, chill in the refrigerator for an hour before serving.