Preheat oven to 375.
Spray a 9x13 pan with baking spray.
In a mixer with a paddle attachment, combine flour, sugar, salt and 14 tbsp of butter, one piece at a time.
Mix until it resembles the texture of wet sand.
May also use food processor.
Set aside 1 ¼ c flour mixture.
Put remaining flour mixture into bottom of pan and press evenly to make bottom layer.
Bake until edges turn brown, about 14-18 minutes.
While it is baking, add brown sugar, oats, and pecans to flour mixture. Mix together.
Work in remaining 2 tbsp of butter with fingers until pea size clumps form.
Set streusel aside.
Mix together jam and fresh berries along with lemon juice in a bowl. Mash with a fork until only some berry pieces remain.
Spread raspberry filling over hot crust; sprinkle streusel topping evenly over filling (do not press into filling).
Return to oven and bake until topping is golden brown and filling is bubbling, about 22-25 minutes.
Let cool to room temperature.