Preheat the oven to 350°F. Grease a 9x13-inch baking dish or line it with parchment paper, leaving enough overhang to easily remove the bars after baking.
In a medium mixing bowl, whisk together 2 cups all purpose flour, 2 teaspoons baking powder, 1 teaspoon baking soda, 2 teaspoons ground cinnamon, and 1 teaspoon salt. Set aside.
In a large mixing bowl, whisk together 1? cups granulated sugar, 1 cup vegetable oil, and 1 can (15 ounces) pure pumpkin until combined.
Add 4 large eggs and whisk until smooth.
Gradually add the dry ingredients to the pumpkin mixture and stir just until combined.
Pour the batter into the prepared baking dish and spread it evenly.
Bake for 30 to 32 minutes, or until a toothpick inserted into the center comes out clean.
Remove from the oven and allow the bars to cool completely before frosting.
For the Cream Cheese Frosting:
In a large mixing bowl, beat 8 ounces softened cream cheese and ½ cup softened butter until light and fluffy.
Add 1 teaspoon vanilla extract and 1½ cups powdered sugar.
Mix on low speed until the frosting is smooth and creamy.
Spread the frosting evenly over the cooled pumpkin bars.
Cut into 12 servings, serve, and enjoy!
Notes
Cover leftover bars tightly and store in the refrigerator for up to 5 days. If you skipped the frosting, cover and store plain pumpkin bars at room temperature for up to 3 days or in the refrigerator for up to 1 week.