1/4 cup fat-free, less-sodium chicken broth  | 
                                                2 tablespoons red wine vinegar  | 
                                                1 teaspoon sugar  | 
                                                1 teaspoon dried oregano  | 
                                                2 teaspoons olive oil  | 
                                                1/2 teaspoon salt  | 
                                                1/2 teaspoon freshly ground black pepper  | 
                                                1 garlic clove, minced  | 
                                                4 (4-ounce) skinless, boneless chicken breast halves  | 
                                                cooking spray  | 
                                                8 cups torn romaine lettuce  | 
                                                1 cup sliced cucumber (about 1 small)  | 
                                                8 pitted kalamata olives, halved  | 
                                                4 plum tomatoes, quartered lengthwise  | 
                                                2 (1/4-inch-thick) slices red onion, separated into rings  | 
                                                1/4 cup (1 ounce) crumbled feta cheese  |