Heat the oil in a Dutch oven over medium heat. Add chicken and next 6 ingredients (chicken through garlic), and cook for 12 minutes. Stir in the broth, juice, salt, and black pepper. Bring to a boil; cover, reduce heat, and simmer 30 minutes. (Can be prepared ahead up to this point.) Remove from heat, and stir in the remaining ingredients except couscous. Serve over couscous, and garnish with parsley, if desired.