Place chicken stock in a saucepan and bring to a boil over medium-high heat. Stir in couscous. Remove saucepan from the heat; cover and let stand for 5 minutes. Fluff couscous with a fork. Cool for 10 minutes.
Meanwhile; make the dressing by combining the olive oil, lemon juice and vinegar in the bowl of a blender or food processor; mix on low until mixture thickens. Stir in rosemary. Season to taste with salt and pepper.
Combine the chicken, cucumber, sun-dried tomatoes and olives in a large bowl. Stir in the couscous, Feta cheese and parsley. Season to taste with salt and pepper.
Toss the salad with half the dressing. Taste and add more dressing as desired or if making the salad in advance add additional dressing just before serving.