Combine vinaigrette ingredients in small bowl; set aside.
Press 2 teaspoons peppercorns evenly onto beef steaks. Place steaks in center of grid over medium, ash-covered coals. Grill steaks, covered, 11 to 14 minutes (over medium heat on preheated gas grill, 12 to 16 minutes) for medium rare (145°F) to medium (160°F) doneness.
Carve steaks into thin slices. Season beef with salt, as desired. Divide salad greens and onions among four serving bowls. Arrange beef on salad. Sprinkle with blue cheese. Drizzle with vinaigrette.