Combine the marshmallows, cornstarch, oil and 3 tablespoons water in a large microwave-safe bowl. Microwave on high in 30-second intervals, stirring in between each, until all the marshmallows are melted, 1 to 2 minutes. Let cool slightly.
Lightly dust a work surface with cornstarch. Turn the dough out onto the work surface and gather it into one lump (if it is too sticky, add 1 teaspoon of cornstarch at a time to reach the level of playdough consistency).
Divide the dough into 4 to 6 balls and place each on a separate paper plate. Add food coloring to each ball and knead it with lightly oiled hands until evenly colored. Once the dough reaches the desired color, PLAY! The dough can be stored in airtight containers for up to 1 week.
Copyright 2018 Television Food Network, G.P. All rights reserved.