Cook orzo as directed. Drain and run cold water over until it's no longer hot. Allow to sit in colander to drain completely.
Whisk dressing ingredients together in a large bowl.
Add drained orzo, vegetables, feta, onion, and parsley to the bowl and toss well. Cover and chill until ready to serve.
Garnish with additional feta and parsley if desired.
Notes
The salad, and any remaining dressing should be refrigerated immediately and be kept in the refrigerator for 2-3 days. If stored longer, there is a risk that the garlic, which has extremely low acidity, may produce botulism, a serious toxin, and this is not a risk worth taking.