1 (8 ounce) tub frozen whipped topping (such as Cool Whip®), thawed
1 ½ cups miniature marshmallows
1 (3.4 ounce) package instant vanilla pudding mix
1 ¾ cups milk
Steps
Preheat the oven to 375 degrees F (190 degrees C).
Sprinkle 3/4 of the crushed graham crackers in the bottom of a 9x13-inch pan; reserve the other 1/4 for topping. Add melted butter over top and press into the pan.
Bake in the preheated oven until set and browned, about 7 minutes. Remove from the oven and let cool.
Mix rhubarb, sugar, cornstarch, and water together in a pot. Cook over medium heat until thick, 5 to 7 minutes. Add red food coloring. Put mixture on top of cooled crust.
Mix frozen whipped topping and marshmallows together in a bowl; spread on top of rhubarb layer.
Mix vanilla pudding with milk in a bowl. Put on top of marshmallow layer. Sprinkle with reserved 1/4 graham crackers. Cool in the refrigerator for about 3 hours.