1. To prepare dressing, combine the first 7 ingredients in a bowl, stirring well, and set aside.
2. To prepare salad, combine 3 tablespoons brown sugar and next 4 ingredients (through garlic) in a large zip-top plastic bag. Add steak to bag; seal. Marinate in refrigerator 4 to 6 hours, turning bag occasionally.
3. Prepare grill.
4. Remove steak from bag, and discard marinade. Place steak on grill rack coated with cooking spray; grill 7 minutes on each side or until desired degree of doneness. Let steak stand 10 minutes; cut steak diagonally across grain into thin slices.
5. Combine lettuce and remaining ingredients in a large bowl. Add dressing; toss gently to coat. Arrange about 1 1/2 cups lettuce mixture on each of 5 plates; top each serving with about 3 ounces steak.