1In small bowl, mix all dressing ingredients with wire whisk until creamy.
2Cut beef steak into 4x1/4-inch strips. In 12-inch nonstick skillet, heat oil over medium-high heat. Add beef to skillet; sprinkle with 1 1/4 teaspoons Greek seasoning. Cook, stirring frequently, until beef is brown. Drain if necessary.
3Divide salad greens among 6 plates. Top each with cucumber, onion, tomato and beef. Serve with dressing.