1Heat oven to 350°F. Grease 15x10x1-inch pan with shortening or cooking spray; lightly flour. In large bowl, beat bar ingredients with electric mixer on low speed until moistened. Beat on medium speed 2 minutes. Spread in pan.
2Bake 20 to 30 minutes or until toothpick inserted in center comes out clean. Cool completely, about 1 hour.
3In small bowl, beat cream cheese and butter on low speed until blended. Beat in 1/2 teaspoon vanilla. Gradually beat in powdered sugar, 1 cup at a time, and 1 to 2 tablespoons milk until frosting is smooth and spreadable. Frost cooled bars. Sprinkle with nutmeg. Refrigerate about 30 minutes or until set. For bars, cut into 8 rows by 6 rows. Store in refrigerator.