In lg. bowl, beat all bar ingredients except raisins or nuts with electric mixer on low speed 30 seconds, scraping bowl frequently. Beat on med. speed 2 min, scrapping bowl occasionally, Stir in raisins. Pour into pan.
Bake 25 to 30 min or until toothpick inserted in center comes out clean. Cool completely, about 2 hrs.
Spread cream cheese frosting on top.