Preheat oven to 350. In a large bowl, combine all crust ingredients at low speed until crumbly. Press mixture evenly in bottom of ungreased 13x9" pan. Bake at 350 for 20 to 30 minutes or until golden brown.
Meanwhile, in a large bowl, combine all filling ingredients except lemon juice; blend well. Stir in 1/4 cup lemon juice. Pour mixture over warm crust. Return to oven & bake an additional 25 to 30 minutes or until top is light golden brown. Cool completely.
Combine frosting ingredients. Add enough lemon juice for desired consistency. Spread over cooled bars. Cut into squares.