Toss scallops with 2 teaspoons soy sauce ( or tamari) in a medium bowl. Set aside.
Place a large, high-sided skillet with a tight-fitting lid over medium heat. Add 1 tablespoon canola oil and quinoa. Cook, stirring constantly, until the quinoa begins to color, 6 to 8 minutes. Add garlic and cook, stirring, until fragrant, about 1 minute more. Add water and salt and bring to a boil. Stir once, cover, and cook over medium heat until the water is absorbed, about 15 minutes. (Do not stir.) Remove from the heat and let stand, covered, for 5 minutes. Stir in snow peas, cover, and let stand for 5 minutes more.
Meanwhile, whisk 3 tablespoons canola oil, the remaining 2 teaspoons soy sauce (or tamari), vinegar, and sesame oil in a large bowl. Add the quinoa and snow peas, scallions, and bell pepper; toss to combine.
Remove the scallops from the marinade and pat dry. Heat a large skillet over medium-high until hot enough to evaporate a drop of water upon contact. Add the remaining 2 teaspoons canola oil and cook the scallops, turning once, until golden and just firm, about 2 minutes total. Gently stir the scallops into the quinoa salad. Serve garnished with cilantro, if desired.
Notes: Be sure to buy "dry" scallops that have not been treated with sodium tripolyphosphate, (STP). STP-treated scallops ("wet" scallops) have been subjected to a chemical bath and are mushy, less flavorful, and won't brown properly.
Find Quinoa, a delicately flavored, protein-rich grain, in natural-foods stores or in the natural-foods sections of many supermarkets. Rinsing removes any residue of saponin, quinoa's natural, bitter protective covering.