Cook the rotini pasta according to package instructions until al dente. Drain and rinse under cold water to cool.
In a large bowl, combine the cooked pasta, diced chicken, cherry tomatoes, cucumber, red onion, olives, feta cheese, and parsley.
In a small bowl, whisk together the olive oil, lemon juice, oregano, salt, and pepper.
Pour the dressing over the pasta salad and toss gently to combine all ingredients evenly.
Chill in the refrigerator for at least 30 minutes before serving to allow flavors to meld.