Rinse trout thoroughly with cold water. Pat dry with paper towels. Place trout in a large heavy-duty, zip-top plastic bag. Combine chicken broth and next 5 ingredients; pour over fish. Seal bag, and marinate in refrigerator 3 hours, turning bag occasionally.
Remove fish from marinade, and discard marinade. Place fish on rack of a broiler pan coated with cooking spray. Place 3 lemon slices in each fish cavity. Broil 5 1/2 inches from heat (with electric oven door partially opened) 4 minutes on each side or until fish flakes easily when tested with a fork. If desired, garnish with lemon wedges and parsley sprigs.