COVER grate of barbecue with foil. Preheat barbecue to medium-high heat. Mix parsley, dressing, tomatoes and garlic; cover. Refrigerate at least 1 hour or up to 24 hours.

CUT four or five slits in top of fish, being careful to not cut through to opposite side of fish. Place on prepared grill grate; cover barbecue with lid.

GRILL 10 to 15 min. or until fish begins to have a milky appearance. Spoon half of the parsley mixture into slits in top of fish; top with remaining parsley mixture. Grill, covered, an additional 10 min. or until fish flakes easily with fork.