Begin by bringing a large pot of water to a rolling boil. Add gluten-free rotini pasta and cook according to the package directions, typically for about 7-9 minutes, until it's al dente. Drain the pasta in a colander and set it aside to cool slightly.

While the rotini pasta is cooking, slice the cucumber and red onion, and chop the yellow bell pepper and grape tomatoes into bite-sized pieces.

Use a box grater to finely grate the parmesan cheese, and cut the mozzarella cheese into small cubes.

In a large mixing bowl, combine the cooled rotini pasta with all the prepared vegetables, cheeses, and pepperoni (if using). Mix gently.

Sprinkle McCormick Salad Supreme Seasoning over the mixed ingredients. Drizzle with Olive Garden Italian dressing and mix evenly.

Stir all the ingredients together until everything is coated with the dressing.

Cover the bowl with plastic wrap or transfer the salad to an airtight container and refrigerate for at least 1 hour.