Combine the quinoa and water in a small saucepan and bring to a boil. Lower to a simmer, cover the saucepan with a lid, and cook for 14 minutes, or until all of the liquid has been absorbed. Let the quinoa rest, covered, for 5 minutes, then fluff with a fork. Set aside.
Meanwhile, combine the red onion, garlic, lemon juice, olive oil, salt, and pepper in a large bowl. Let the mixture stand for 10 minutes or until the onions have softened slightly.
Drain and rinse your beans. When it comes to the chickpeas, I like to remove the skins because I’m obsessive like that. To do this, place the drained chickpeas between two sheets of paper towel and rub lightly. This will loosen the skins, which you can then pick off and discard. (Yes, this is optional, but it’s not that hard, so you should probably just do it.)
Add the chickpeas, black beans, edamame, cooked quinoa, parsley and scallions to the bowl with the dressing. Toss to combine.
Cover and refrigerate your salad for at least half an hour to let the flavors mingle. Serve cold or at room temperature.