For the parsley vinaigrette: Into small bowl, measure vinaigrette ingredients. Mix with wire whisk or fork until well blended; set aside. For the salad: In 3-quart saucepan, place potatoes and enough water to cover; heat to boiling over high heat. Reduce heat to low; simmer 10 to 12 minutes or until potatoes are fork-tender.
Meanwhile, in 2-quart saucepan, place eggs and enough cold water to cover by 1 inch; heat to boiling over high heat. Immediately remove saucepan from heat and cover tightly; let stand 15 minutes. Pour off hot water; run cold water over eggs to cool. Remove shells and cut each egg into wedges.
When potatoes are done, with slotted spoon, remove potatoes from water to colander to drain. To same water in saucepan, add beans; heat to boiling over high heat. Reduce heat to low; simmer 5 to 10 minutes or until tender-crisp. Drain beans; rinse with cold running water to stop cooking; drain again.
In large bowl, toss greens with half of vinaigrette. Place greens on large platter. Cut each potato in half or into quarters if large; transfer to platter with greens. Arrange beans, eggs, cucumber, tuna, tomatoes, and olives in separate piles on same platter; drizzle with remaining vinaigrette.
Recipe courtesy of Good Housekeeping, 2012