Prepare the dressing by mixing everything in a jar with a tight-fitting lid. Store it in the refrigerator, and shake well prior to using. The flavor of the dressing will improve over several hours or overnight; prepare it ahead if possible. The dressing will keep for a week or more in the fridge.
Cook the pasta according to the package directions. Drain well, and toss with a tablespoon or so of the dressing to keep the noodles from sticking as they cool and while you prepare the rest of the ingredients.
When the pasta is cool, place it in a serving bowl, and add the tomatoes, cucumber, olives, onion, and parsley. Drizzle with 1/3 to 1/2 cup of the dressing and toss well. (Reserve any leftover dressing to pass at the table or save for future use.) Add the crumbled feta, toss again, and enjoy.
Notes
In a pinch, feel free to substitute your favorite bottled Greek dressing, although this recipe adds great flavor and is easy to make!