I make these every year for Christmas, and they are a fan favorite! It makes a bunch, so freeze them and enjoy for many months.
Preheat oven to 350 degrees F.
In a medium bowl, mix the eggs, sugar, oil, and pumpkin with an electric mixer until light and fluffy. Sift together the flour, baking powder, baking soda, cinnamon and salt. Stir into the pumpkin mixture until thoroughly combined.
Spread the batter evenly into an ungreased 10x15 inch jellyroll pan. Bake for 25 to 30 minutes in preheated oven. Cool before frosting.
To make the frosting, cream together the cream cheese and butter. Stir in vanilla. Add confectioners' sugar a little at a time, beating until mixture is smooth. Spread evenly on top of the cooled bars. Cut into squares.