Adjust the oven rack to middle position; heat oven to 375 degrees. Cut an 18-inch length foil and fit into length of 13 x 9-inch baking dish, pushing into corners and up sides of pan; allow excess to overhang pan edges. Cut 14-inch length of foil and fit into width of baking pan in same manner. Spray foil-lined pan with nonstick cooking spray.

In a mixer fitted with a paddle attachment, mix flour, granulated sugar, and salt at low speed until combined, about 5 seconds. With machine on low, add 16 tablespoons of butter, 1 piece at a time; then continue mixing on low until mixture resembles damp sand, 1 to 1 ½ minutes longer.

Measure 1 ¼ cups of the flour mixture into medium bowl and set aside; distribute the remaining flour mixture evenly in bottom of prepared baking pan. Using your hands or the flat-bottomed measuring cup, press the mixture into even layer to form bottom crust. Bake until edges begin to brown, 14 to 18 minutes.

While the crust is baking, add brown sugar, oats and nuts to the reserved flour mixture; toss to combine. Work in the remaining 2 tablespoons butter by rubbing the mixture between your fingers until butter is fully incorporated. Pinch mixture with fingers to create hazelnut-sized clumps; set streusel aside.

Combine preserves, raspberries, and lemon juice in small bowl; mash with a fork until combined but some berry pieces remain.

Spread filling evenly over hot crust; sprinkle the streusel topping evenly over filling. Return pan to the oven and bake until topping is a deep golden brown and filling is bubbling, 22 to 25 minutes. Cool to room temperature on wire rack, 1 to 2 hours; remove from baking pan by lifting foil extensions. Cut them into squares.