Heat the 2 teaspoons olive oil in a medium saucepan over medium heat. Add the garlic and saute until fragrant, stirring, about 1 minute. Add the quinoa and vegetable broth (or water) and bring to a boil. Reduce the heat, cover, and simmer until the liquid has been absorbed, about 12-16 minutes. Remove from the heat.
While the quinoa cooks, prepare the lime vinaigrette. In a small bowl or jar, combine the dressing ingredients. Whisk (or shake in a jar with a lid) until well combined.
Transfer the cooked quinoa to a large bowl and stir in the corn, black beans, bell pepper, green onions and cilantro. Add the dressing and stir gently to combine. Taste and adjust seasonings as necessary.
Serve salad warm or cold, with guacamole or sliced avocado if desired.
Quinoa salad can be stored for 3-4 days in the refrigerator.