1Preheat the oven to 375 degrees F and line a 9 x 13 inch pan with foil that is coated with cooking spray.
2Using a stand mixer, hand mixer or food processor, mix the flour, granulated sugar and salt. Add one cup of the butter, one piece at a time, while mixing at low speed until the mixture resembles damp sand.
3Measure 1 ¼ cup of the mixture into a bowl and set aside. Distribute the remaining flour and butter mixture evenly in the pan. Firmly press the mixture into an even layer on the bottom of the pan and bake for about 14-18 minutes, or until the edges begin to brown.
4While the crust is baking, add brown sugar and oats to the reserved flour mixture. Toss to combine. Add the remained 2 tablespoons of butter to the mixture until combined. Pinch the mixture to form clumps and set aside.
5Combine the preserves, fresh raspberries and lemon juice in a small bowl. Use a fork to mash the mixture until combined and just a few berry pieces remain.
6Once the crust has browned and rested outside of the oven for about five minutes, pour the raspberry mixture on top and spread to form an even layer. Sprinkle the streusel topping on top (do not press into the filling).
7Return the pan to the oven and bake for 22-25 minutes until the filling is bubbling and the topping is a deep golden brown.
8Allow the bars to cool on a wire rack for at least 1 hour before cutting.