PREPARE cake batter and bake as directed on package for 13x9-inch pan. Cool cake in pan 15 min. Pierce cake with large fork at 1/2-inch intervals.
ADD boiling water to gelatin mixes; stir 2 min. until completely dissolved. Stir in strawberries; spoon over cake. Refrigerate 2 hours.
FROST with COOL WHIP. Refrigerate 1 hour.