Preheat your oven to 350°F (175°C) and prepare a 9x13-inch baking pan by greasing it.

In a large mixing bowl, mix together 4 eggs, 2 cups sugar, 1 cup vegetable oil, and 1 cup canned pumpkin on medium speed for 1.5 minutes.

In a separate bowl, whisk together 2 cups all-purpose flour, 2 teaspoons baking powder, 1 teaspoon cinnamon, 1 teaspoon baking soda, and 1/2 teaspoon salt.

Gradually add the dry mixture to the wet mixture, mixing on low speed until just combined.

Pour the batter into the greased baking pan and spread evenly. Bake for approximately 30 minutes or until a toothpick comes out clean.

Let the bars cool completely in the pan on a wire rack before frosting.

To make the icing, beat together 8 ounces cream cheese and 1/2 cup butter until smooth, then gradually add 4 cups powdered sugar and 1 teaspoon vanilla.

Frost the cooled pumpkin bars with the cream cheese icing and serve.