Prepare grill or broiler.
Combine the chicken broth, red wine vinegar, sugar, salt, oregano and olive oil in a small bowl.
Brush the chicken with 2 tablespoons dressing; set remaining dressing aside.
Place chicken on grill rack or broiler pan coated with cooking spray; cook for 5 minutes on each side or until chicken is done.
Cut into 1/4-inch-thick slices.
In a large bowl, combine lettuce, tomatoes, onions, cucumbers, feta cheese, olives and scallions.
Add remaining dressing, basil, garlic, thyme, black pepper and cayenne pepper.
Top with sliced chicken.
Serve immediately.