Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain.
Heat olive oil in a large skillet over medium heat. Saute garlic for 2 minutes, then stir in chicken, and cook until no longer pink, and juices run clear. Remove from skillet, and set aside. Heat 1 tablespoon olive oil. Saute red onion, green bell pepper, red bell pepper, yellow bell pepper and yellow squash until tender.
In a large bowl, combine pasta, chicken, pepper mixture, basil and balsamic vinegar. Toss until evenly distributed.
