Preheat the oven to 350°F. Prepare the baking dish with parchment paper, leaving an overhang on both sides.
In a bowl, Mix together the oat flour, oats, brown sugar, baking powder, and salt. Add the melted butter and mix until it is thoroughly combined.
Transfer two-thirds of the oat mixture into the baking dish and press it down firmly.
Pour the raspberry mixture over the oat base. Crumble the remaining oat mixture on top of the raspberry mixture in an even layer.
Bake for 20 to 25 minutes.
Allow the oat bars to cool at room temperature, cut them into squares.
You can store in the refrigerator for up to 5 days.