Heat oven to 350 degrees F. Line an 8-inch square baking pan with parchment paper, leaving some overhang for easy removal later.
In medium bowl, stir together melted butter and brown sugar until smooth. Stir in egg until fully mixed.
In separate large bowl, stir flour, salt, baking powder and oats together. Add brown sugar mixture to flour mixture to make crust mix, stirring until fully blended. Press 2/3 of the oatmeal crust mix evenly into the bottom of the prepared pan.
Spread raspberry filling evenly over oatmeal crust. Sprinkle ½ cup blueberries over raspberry filling. Crumble remaining crust mixture over the blueberries.
Bake 30-35 minutes or until the top is golden and the edges are bubbling. Let it cool completely in the pan before lifting it out with the parchment paper handles to cut into bars.