Chop cucumber, zucchini, yellow squash and red bell pepper into 1-inch pieces. Set aside.
In a 4 quart pot of boiling salted water, cook the tortellini according to package instructions (usually 7-9 minutes). Remove pot from heat, strain tortellini and rinse with cold water. Add to a large bowl. Stir in chopped vegetables and Italian salad dressing. Season with Italian seasoning, salt and pepper. Top with freshly grated Parmesan cheese.
Cover bowl and chill up to 1 day, or serve immediately over spinach.