Rinse the quinoa in a fine mesh strainer under running water and set aside to drain. In a large soup pot, heat the oil. Then, add the onions, garlic and salt and cook over medium heat for 5 minutes, stirring every now and then.
Add the drained quinoa, chicken, bell pepper, coriander, cumin, oregano, chicken stock and tomatoes, stirring to combine. Bring to a boil; then, lower the heat and simmer for about 10 minutes.
Add the squash and simmer for an additional 15-20 minutes or until the vegetables are fork tender. If desired, stir in the lemon juice. Serve and enjoy!