Cook pasta as directed on package, adding asparagus for last 2 minutes of cooking; drain. Rinse with cold water; drain.
In tightly covered container, shake oil, vinegar, mustard and garlic salt.
In large bowl, toss pasta, asparagus, bell pepper, tomatoes and oil mixture. Cover and refrigerate at least 30 minutes to blend flavors but no longer than 24 hours. Serve with pepper.