Cook 1 cup quinoa according to package directions. Rinse it first. To do this, just place the quinoa in a fine mesh strainer and rinse it under water for a few minutes.
When the quinoa is done cooking, fluff it with a fork, transfer it to a large bowl, and allow it to cool completely (about 15 minutes).
In a small bowl whisk together lime juice, olive oil, ground cumin, black pepper and salt.
When the quinoa has cooled, add in black beans, corn, red bell pepper, chopped green onions, and cilantro.
Stir in dressing and toss to coat.
Cover and refrigerate for at least an hour before serving.