Boil green beans in large pot. Let cook 2 to 3 minutes depending on thickness of beans. Strain and rinse with cold water to stop cooking process. Trim fennel and cut into 1/4-inch thick rounds. Cut bell pepper in 1/4-inch strips. Refrigerate, covered, until service.

Whisk together vinegar and mustard in small bowl. Mash garlic and salt together with back of fork to make a paste. Whisk into vinegar. Slowly whisk in oil until emulsified. Cover and refrigerate.

When ready to serve, arrange lettuce leaves on a large platter. Toss green beans, bell peppers and fennel with dressing and spread over lettuce.