Start by preheating your oven to 350°F (175°C). Grease a 13×9-inch baking pan or line it with parchment paper. Preparing the pan properly helps the bars bake evenly and release easily after cooling.
In a large mixing bowl, beat together the softened butter, oil, brown sugar, granulated sugar, and pumpkin purée. Mix until smooth and creamy. This mixture gives the bars their soft, moist texture and rich flavor.
Stir in the egg, vanilla extract, salt, pumpkin pie spice, and baking soda. Mix until everything is well blended. This step ensures even flavor and just the right rise while baking.
Add the flour and gently mix until the batter comes together. Fold in the chocolate chips but save a handful to sprinkle over the top. This keeps the bars tender and adds chocolate in every bite.
Pour the batter into your prepared baking pan and smooth the top. Bake for 25–30 minutes or until a toothpick inserted in the center comes out clean or with soft crumbs. Allow the bars to cool completely to help them set and slice cleanly.