Preheat oven to 350 degrees. In a large mixing bowl, cream oil, eggs and sugar. Add remaining cookie ingredients and mix well. Pour batter into an ungreased 15x10 inch jelly roll pan. Bake at 350 degrees for 20 to 25 minutes. Cool completely and frost with cream cheese frosting.
To make frosting, cream together all the frosting ingredients. Spread on cooled, uncut cookies. After frosting has set, cut into equal size bars.
Store any leftover bars, covered, in the refrigerator. These moist pumpkin bars will keep up to a week, covered, in the refrigerator.
Variation: Add 1/2 cup chopped walnuts or raisins to the recipe.
Yield: 36 pieces.