1Place 3/4 cup of the blueberries, 2 tablespoons of the marinade, water and lemon juice in food processor. Cover. Process until smooth. Refrigerate dressing until ready to serve.
2Place steak in large resealable plastic bag or glass dish. Add 1/4 cup of the remaining marinade; turn to coat well. Refrigerate 30 minutes or longer for extra flavor. Remove steak from marinade. Discard any remaining marinade.
3Grill steak over medium-high heat 6 to 8 minutes per side or until desired doneness, brushing with remaining 2 tablespoons marinade. Cut steak into thin slices.
4 Divide salad greens evenly among 4 serving plates. Top each with steak slices. Sprinkle with remaining 3/4 cup blueberries, feta and onion. Serve with dressing.