Beat pudding mix and milk in medium bowl with whisk 2 min. Stir in 1-1/2 cups COOL WHIP and bananas.
Spread 1 rounded Tbsp. pudding mixture onto each of 20 graham squares. Stack grahams together, then stand on edge on serving platter to make 8-1/2-inch loaf. Frost with remaining COOL WHIP. Crush remaining graham squares; sprinkle over loaf.