Preheat the oven to 350°F (175°C). Grease a 9x13-inch baking pan.
In a large mixing bowl, combine the vegetable oil, granulated sugar, pumpkin puree, and eggs. Mix until well combined.
In a separate bowl, whisk together the flour, baking powder, ground cinnamon, salt, and baking soda.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Pour the batter into the prepared baking pan and spread it evenly.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the pumpkin bars to cool completely in the pan.
Meanwhile, prepare the cream cheese frosting. In a large mixing bowl, beat the softened cream cheese and butter until smooth and creamy.
Gradually add the powdered sugar, beating until smooth. Add the vanilla extract and mix until combined.
Once the pumpkin bars are completely cool, spread the cream cheese frosting evenly over the top.
Cut into bars and serve.