Cook the spaghetti according to the package instructions until al dente. Drain and rinse under cold water to stop the cooking process. Allow to cool completely.
Prepare the Vegetables:
While the spaghetti is cooling, prepare the vegetables: halve the cherry tomatoes, dice the cucumber, red and green bell peppers, and finely chop the red onion.
Mix the Salad:
In a large mixing bowl, combine the cooled spaghetti, cherry tomatoes, cucumber, bell peppers, red onion, and sliced black olives.
Add Dressing and Seasoning:
Pour the Italian dressing over the salad. Add the grated Parmesan cheese, Italian seasoning, salt, and pepper. Toss everything together until well combined.
Chill and Serve:
Cover the salad and refrigerate for at least 1 hour before serving to allow the flavors to meld together. Garnish with fresh parsley or basil if desired.
Enjoy:
Serve chilled and enjoy your easy California spaghetti salad!