Preheat oven to 350 degrees. Grease a 9-by-13-inch baking pan and set aside. In a medium bowl, whisk together flour, pumpkin pie spice, baking soda, and salt; set aside.
With a stand or electric mixer, cream butter and sugar on medium-high speed until smooth; beat in egg and vanilla until combined. Add pumpkin puree and mix well. The mixture will look somewhat curdled. Reduce speed to low, and mix in dry ingredients until just combined. Fold in chocolate chips.
Spread batter evenly in prepared pan. Bake bars for 35-40 minutes or until edges begin to pull away from sides of pan and a toothpick inserted in center comes out with just a few moist crumbs attached.
Cool bars completely in pan. Cut into squares and serve.