Cook tortellini according to package directions. Drain and rinse under cold water to cool.
In a large bowl, combine the cooked tortellini, pepperoni, cherry tomatoes, basil, mozzarella, olives, and red onion.
Pour the Italian dressing over the salad and toss until everything is well coated.
Season with salt and pepper to taste.
Chill for at least 1 hour before serving to let the flavors meld.