Mix flour, xanthan gum, brown sugar, and 1/4 cup granulated sugar in medium bowl; cut in butter with pastry blender or 2 knives until mixture resembles coarse crumbs.
Stir in oats and pecans. Reserve 1 cup of oat mixture; press remaining mixture onto bottom of pan.
Bake 15 minutes.
Pumpkin Filling
Beat cream cheese, 1/2 cup granulated sugar, eggs, pumpkin and pumpkin pie spice in a small bowl with electric mixer on medium speed until well blended.
Pour over crust; sprinkle with reserved crumb mixture.
Bake 25 minutes. Cool completely.
Cut into 24 bars. Serve with ice cream or whipped topping.
Store leftover bars in tightly covered container in the refrigerator.