Cook shells to desired doneness as directed on package. Drain; rinse with cold water.

In medium bowl, combine cooked shells, shrimp, peas and onion. In small bowl, combine yogurt, lemon juice, oil, thyme, salt and pepper; blend well. Spoon dressing over macaroni-shrimp mixture; toss gently. Cover; refrigerate 45 minutes or until chilled.

To serve, spoon mixture into 6 Cucumber Cups(see recipe), or onto lettuce leaves. Just before serving, lightly squeeze lemon juice over salad. Garnish with fresh thyme, if desired.