Heat oil in a large skillet over medium-high heat. Add garlic and saute until fragrant, about 1 minute.
Add black beans, tomatoes, corn, quinoa, chicken broth, chili powder, cumin, salt, and black pepper to skillet.
Bring to a boil, cover, reduce heat to low, and simmer about 20 minutes or until most of the liquid is absorbed and quinoa is tender.
Serve over spinach and top with avocado slices. Add your favorite low-fat spicy dressing, if desired.