Fill a large pot with salted water and bring it to a boil.
While waiting on the water, mince the garlic. In a jar or small bowl, combine the garlic, olive oil, red wine vinegar, Italian seasoning, Dijon mustard, salt, and pepper. Shake well or whisk until fully blended.
Transfer half of the dressing (about ½ cup) into a large mixing bowl. Set the rest aside for later.
Finely dice the red onion and stir it into the dressing in the bowl. Separate the layers so they soften in the vinegar mixture.
Once the water is boiling, cook the farfalle according to package directions until al dente, about 11 to 13 minutes. Drain, rinse with cold water to stop the cooking, then drain again thoroughly.
While the pasta is cooking, prep the vegetables:
Halve the grape tomatoes.
Remove the core from the bell pepper and dice it.
Trim the ends of the zucchini and squash, cut them lengthwise into quarters, and slice into ¼-inch thick pieces.
Drain the canned black olives.
Add all the vegetables and olives to the bowl with the onion and dressing. Stir to coat.
Add the cooled, drained pasta to the bowl. Toss until everything is evenly mixed and coated in dressing.
Right before serving, pour in the remaining dressing and top with chopped parsley. Toss again to refresh the flavor.