Bring potatoes to a boil in a large pot of salted water and cook until tender, about 15 min. Add green beans to pot during last 2 min. of cooking to tenderize beans. Drain vegetables and run under cold water until cold.
Cut potatoes into quarters and arrange in a section on a large platter. Fill rest of platter with sections of beans, lettuce, tomatoes, eggs and red onion.
To make the vinaigrette, whisk together olives, lemon juice, mustard, pepper and olive oil and then pour over salad.
Double this vinaigrette recipe and use it as a flavourful marinade for fish or chicken.