Boil pasta according to package directions and drain when cooked. Pasta should be cooked to firm or al dente.
While pasta is cooking, prepare rest of ingredients, cutting up meats, cheese and veggies. You can substitute any veggies you like. I add broccoli and cauliflower, onions and celery or sometimes I make it with pepperincini, marinated artichoke hearts, tomatoes, roasted red peppers.
Place drained, slightly cooled pasta in large bowl. Add meat, cheese and veggies to drained pasta. Then add package of Italian dressing mix. Mix well and cover with plastic wrap. Refrigerate for at least one hour.
Make dressing by combining oil, balsamic vinegar, oregano, parsley, grated parm cheese, salt and pepper. Whisk until ingredients are well combined. (note: I didn't think the dressing was acidic enough, so I added a little wine vinegar to the mixture)
Just before serving, pour dressing over pasta mixture. (Of course, you can pour dressing over pasta mixture after refrigerating it for 1 hour -- I think it has a better flavor, since the flavors have had time to marry when I let it sit over night. -- That's just my opinion.)