Cook pasta according to package directions; drain. Rinse pasta with cold water; drain. In a large bowl, combine the pasta, tomatoes, feta cheese, salad dressing, green onions, and olives. Cover and chill in the refrigerator for at least 2 hours or up to 24 hours.
To serve, arrange spinach on a large serving platter; spoon pasta mixture over spinach. Sprinkle with cracked pepper. Makes 8 to 12 side-dish servings.