Preheat oven to 325 degrees Fahrenheit. Line a 9-inch square pan with parchment paper leaving overhang on two sides.
Mix graham cracker crumbs, sugar, and melted butter. Press firmly into the pan. Bake 10 minutes. Turn oven up to 350 degrees Fahrenheit.
Beat cream cheese and sugar until smooth, about 1 minute. Add eggs one at a time on low speed. Beat in vanilla, pumpkin, sour cream, cinnamon, pumpkin pie spice, and salt until smooth. Pour over warm crust.
Mix oats, brown sugar, flour, and cinnamon. Cut in cold butter until crumbly. Sprinkle evenly over filling.
Bake 40 to 45 minutes. After 30 minutes, loosely cover with foil. Bars are done when edges are set and center jiggles slightly.
Cool at room temperature 1 hour. Refrigerate at least 3 hours or overnight.
Lift out of pan, slice into 12 to 16 bars with a clean knife. Dust with powdered sugar or drizzle with icing before serving.