In a large soup pot or dutch oven, heat the olive oil over medium high heat and add the onion. Cook the onion for 2-3 minutes, or until soft and translucent, stirring occasionally. Stir in the minced garlic and continue to cook for an additional minute, until garlic is nice and fragrant.
Stir in the lemon zest, lemon juice, chicken or vegetable broth, chicken breasts, salt and pepper and crushed red pepper. Turn heat to high, cover the pot and bring to a boil. Once boiling, reduce heat to medium low and allow soup to simmer for 5-10 minutes more.
Stir in the couscous and artichoke hearts and cook for an additional 5 minutes. Using tongs, remove the chicken breasts from the pot and shred it with a fork (or simple cut into small bite size pieces). Return chicken to the pot and turn off the heat. Stir in the crumbled feta and chopped green onions directly into the pot, or reserve and garnish each individual bowl separately.