Prepare the chicken by shredding or dicing it into bite-sized pieces. If using raw chicken, boil, grill, or bake until fully cooked, then let cool.
If using canned chickpeas, drain and rinse them under cold water. If using dried chickpeas, soak overnight and cook in boiling water until tender.
Chop the cherry tomatoes, cucumber, red onion, and parsley.
In a large mixing bowl, combine the chicken, chickpeas, cherry tomatoes, cucumber, red onion, and parsley. Add feta cheese if using.
In a small bowl, whisk together olive oil, lemon juice, garlic powder, salt, and pepper. Pour over the salad mixture and toss gently.
Chill the salad in the refrigerator for at least 30 minutes before serving.