Bring quinoa and water to a boil in a medium saucepan. Reduce heat to medium-low, cover, and simmer 15 to 20 minutes, or until all the water is absorbed. Remove from the heat, and set aside to cool (at least 15 minutes). Fluff the grains before assembling the salad.
If using frozen corn, run under warm water to thaw. If using canned corn, drain thoroughly before adding to salad.
In a large serving bowl, combine corn, black beans, red bell pepper, green onion, and cilantro. Mix in cooled quinoa.
Add remaining ingredients and toss well to combine. Serve at room temperature or chilled.
Note: For a creamy texture and extra nutrition, add one medium diced ripe avocado.