In a medium saucepan bring a large amount of water to boiling. Add pasta and frozen mixed peas and carrots. Return to boiling, then reduce heat slightly. Boil, uncovered, for 5 to 8 minutes or till pasta and carrots are tender. Immediately drain mixture in a colander, then rinse with cold water and drain again.
In a medium mixing bowl stir together pasta, peas and carrots, ham, and green onions. In a small mixing bowl stir together yogurt, cucumber dressing, and dillweed. Pour yogurt mixture over pasta and vegetable mixture. Toss till well coated. Cover and chill for at least 4 hours.
To serve, arrange the tomato slices and green pepper on 4 lettuce-lined salad plates. Stir the pasta mixture and divide mixture among plates.
