Bring a small covered pot of water to a boil over high heat. Stir in the edamame and cook for about a minute, then drain. Run under cold water, gently tossing while the cold water runs over the edamame to cool them down. Drain again, then turn them into a bowl.
Seed and coarsely dice the bell peppers, then add them to the bowl. Finely chop the red onion and add