Prepare grill. Sprinkle steaks evenly with salt and pepper. Put steaks on grill rack coated with cooking spray. Grill 5 minutes on each side or til desired degree of doneness. let stand 10 minutes before slicing.
While steak stands, mix lettuce, tomato and cucumber in large bowl; divide evenly among 4 plates. In small bowl, mix sour cream, red onion and next 4 ingredients, stirring with a whisk til well blended.
Top salads with steak slices. Drizzle salads evenly with dressing. Makes 4 servings.