Bring a large pot of lightly salted water to a boil.
Cook pasta in the boiling water, stirring occasionally until cooked to al dente according to instructions on package. Drain and rinse under cold water to stop the cooking process.
Whisk together the Italian dressing, onion powder, fresh parsley and mayonnaise in a large mixing bowl. Stir pasta, chicken sausage, bacon, cheese, cherry tomatoes, and avocado into dressing until evenly coated.
Season with salt and pepper.
Let sit in the refrigerator for at least a couple of hours for flavors to come together before serving. If letting sit overnight, you may need some more Italian dressing added before serving because the pasta will soak some of it up. Toss and serve cold or at room temperature.