Follow package directions to cook orzo.
While orzo cooks, prep tomatoes, zucchini, squash, mozzarella, basil and pine nuts. Set aside.
Combine dressing ingredients (except olive oil) in small bowl; slowly whisk in oil to emulsify/thicken. OR, toss all ingredients into a lidded jar and shake vigorously. Set aside until ready to use.
When orzo is cooked al dente, drain in a colander and allow to cool about 15 minutes. Run a spoon through it every once in a while to cool it down.
When relatively cool (i.e., still a little warm to the touch), add orzo to a large mixing bowl, along with balsamic dressing, tomatoes, squash, zucchini, & mozzarella. Taste for seasoning and adjust according to preference.
Add pine nuts and basil just before serving, so basil does not turn brown and nuts stay crunchy.