Bring a large pot of salted water to a boil. Cook the pasta according to package directions until al dente. Drain and rinse under cold water to cool.
In a large bowl, combine the cooled pasta, cherry tomatoes, red onion, black olives, pepperoncini, feta cheese, and parsley.
In a small bowl, whisk together olive oil, red wine vinegar, Dijon mustard, garlic, salt, and pepper to make the dressing.
Pour the dressing over the pasta mixture and toss gently to combine. Cover and refrigerate for at least 1 hour before serving to allow flavors to meld.
Notes
Best served chilled. Can be made ahead and stored in the refrigerator for up to 3 days.