Rinse under cold running water until water runs clear.
Mix quinoa with 2 cups water and salt in heavy medium saucepan then bring to boil.
Reduce heat and simmer covered until quinoa is just tender and almost all the water is absorbed, about 15-20 minutes.
Drain, spread quinoa on a baking sheet to cool then fluff with fork.
Grill bell peppers on a well-oiled hot rack until slightly softened, about 4 minutes on each side.
Place in paper bag to cool then remove skin.
Cut bell peppers crosswise into thin strips.
Whisk together oil, lime juice, soy sauce, and cumin in a large bowl and stir in quinoa, bell peppers, cilantro, scallions, add salt and pepper to taste.