Cook Green Beans in large pot of boiling salted water until crisp-tender, about 3 minutes. Drain; rinse with cold water and drain well. Pat dry, then wrap in paper towels. Place in plastic bag and refrigerate.(Can be prepared 1 day ahead.)
Combine beans, tomatoes, onion and basil in serving bowl. Whisk oil, vinegar and sugar in small bowl to blend. Season dressing with salt and pepper. Add dressing to vegetables; toss to coat. Cover, chill at least 1 hour and up to 4 hours, tossing occasionally. Serve salad cold or at room temperature.
