Heat oven to 350F. In large bowl, combine all crust ingredients (first 4 ingredients) at low speed until crumbly. Press in bottom of ungreased 13x9-inch pan. Bake at 350F, for 10 minutes.
Meanwhile, in small bowl beat egg whites at medium speed until soft peaks form. Gradually add sugar 1 tbsp. at a time, beating at high speed until glossy peaks form and sugar is dissolved. Spread lemon filling over partially baked crust; spread meringue over lemon filling.
Bake an additional 15 to 25 minutes or until meringue is light golden brown. Cool completely; cut into squares. Garnish with citrus twists, if desired 12 servings