Heat the canola oil in a saucepan over medium heat. Cook and stir the garlic and 1/4 cup onion in the hot oil until the onion has softened and turned translucent, about 5 minutes. Pour in the water, 2 teaspoons salt, and 1/4 teaspoon black pepper and bring to a boil; stir the quinoa into the mixture, reduce heat to medium-low, and cover. Simmer until the quinoa is tender, about 20 minutes. Drain any remaining water from the quinoa with a mesh strainer and transfer to a large mixing bowl. Refrigerate until cold.
Stir the tomato, carrots, bell pepper, cucumber, corn, and 1/4 cup red onion into the chilled quinoa. Season with cilantro, mint, 1 teaspoon salt, and 1/4 teaspoon black pepper. Drizzle the olive oil and balsamic vinegar over the salad; gently stir until evenly mixed.