In a large non-stick skillet, add oil, turn to medium-high heat, add chicken and brown on both sides, about 5 minutes per side. Remove chicken and place on a plate lined with a paper towel. Add onion to skillet, reduce heat to medium-low, sauté until tender, about 4 minutes. Add garlic and sauté 1 additional minute.
Return chicken to skillet and add the remaining ingredients. Cover, and cook until chicken is cooked through and quinoa is tender and absorbed most of the liquid, about 15 minutes.