Cook the rotini pasta according to package instructions until al dente. Drain and rinse under cold water to cool.
In a large mixing bowl, combine the cooked pasta, diced chicken, cherry tomatoes, cucumber, red onion, olives, feta cheese, and parsley.
In a separate small bowl, whisk together the olive oil, red wine vinegar, oregano, garlic powder, salt, and pepper.
Pour the dressing over the pasta salad and toss gently to combine all ingredients evenly.
Cover the salad and refrigerate for at least 30 minutes to allow flavors to meld.
Serve chilled or at room temperature, garnished with additional parsley if desired.