Preheat oven to 350. Line a 13×9 pan with parchment paper or grease generously (I prefer parchment)
Crumble
In a medium bowl, mix flour, brown sugar, and sugar. Cut in butter until mixture resembles coarse crumbs, then stir in oats and pecans. Reserve 1 cup for topping, then press the remaining mixture into the bottom of the pan. Bake for 15 minutes.
Filling
While the crust is baking, prepare the filling. In the bowl of a mixer, add cream cheese, pumpkin, eggs, sugar, and pumpkin pie spice, and beat on medium speed until well blended. Pour over the cooked crust, sprinkle with the reserved crumb mixture, and press down. Bake for 23-25 minutes. The middle may look underdone.
Before slicing, cool for 1 hour, then cover the baking dish with plastic wrap and refrigerate for 3 hours. Once chilled, lift bars out of the pan and cut into squares.