Cook green beans in boiling water 4 minutes or until crisp-tender. Drain and rinse with cold water; drain well.
Combine oil, next 6 ingredients, and 1/4 teaspoon salt in a bowl; stir with a whisk. Stir in beans, chickpeas, and tomatoes; toss. Sprinkle with walnuts, cheese, and olives.
Sprinkle tuna with remaining 1/4 teaspoon salt and pepper. Heat a grill pan over medium-high heat. Coat pan with cooking spray. Add tuna to pan; cook 3 minutes on each side or until desired degree of doneness. Divide bean mixture evenly among 4 plates; top with sliced tuna.
MyRecipes is working with Let's Move!, the Partnership for a Healthier America, and USDA's MyPlate to give anyone looking for healthier options access to a trove of recipes that will help them create healthy, tasty plates. For more information about creating a healthy plate, visit www.choosemyplate.gov.