Fill a large pot with lightly salted water and bring to a rolling boil over high heat. Once the water is boiling, stir in the pasta, and return to a boil. Cook the pasta uncovered, stirring occasionally, until the pasta has cooked through, but is still firm to the bite, about 10 minutes. Drain well in a colander set in the sink, rinse with cool water and place in a large bowl.
Place a steamer insert into a saucepan, and fill with water to just below the bottom of the steamer. Cover, and bring the water to a boil over high heat. Add the broccoli , recover, and steam until just tender, 2 to 6 minutes depending on thickness. Rinse the broccoli with cold water, finely chop, and add to pasta.
Stir in the garlic, red onion, artichoke hearts, kalamata olives, roasted red peppers, Roma tomatoes, sun-dried tomatoes, zucchini, cucumber, and yellow pepper and combine well.
Cut the avocados in half, remove the pit, and remove from the skin with a large spoon. Cut the avocados into large pieces, place in a small bowl and mash well with a fork. Slowly whisk in the Greek dressing until well combined. Pour the Greek-avocado dressing into the pasta salad and gently toss. Refrigerate for at least one hour before serving.