In a skillet, saute onion and garlic in oil until tender. Stir in tomatoes, wine, olives, parsley and salt. Bring to a boil. Cook, uncovered, for 5 minutes.
Add fillets. Reduce heat; cover and simmer for 12-15 minutes or until fish flakes easily with a fork. Remove fish to serving plates; keep warm. Simmer sauce, uncovered, for about 4 minutes or until it reaches desired thickness.