Place flour in a zip-top plastic bag; add scallops. Seal and shake to coat. Remove scallops from bag, shaking off excess flour; set aside.
Melt margarine in a large nonstick skillet over medium heat. Add onion, and sauté 3 minutes or until lightly browned. Add shallots and garlic, and sauté 1 minute. Add scallops, wine, and next 4 ingredients (wine through bay leaf). Cover, reduce heat, and simmer 4 minutes. Uncover and bring to a boil, and cook 1 minute. Discard bay leaf. Divide scallop mixture evenly among 4 individual gratin dishes. Top each with 1 tablespoon cheese; broil 30 seconds or until cheese melts. Serve immediately.
Note: Substitute 3/4 cup low-salt chicken broth for wine, if desired.