1. Prepare grill.
2. Coat a large nonstick skillet with cooking spray; place over medium-high heat until hot. Add bell pepper, onion, and garlic; cook, stirring constantly, until tender. Stir in tomato and next 5 ingredients; cook until mixture is thoroughly heated, stirring often. Set aside, and keep warm.
3. Brush fillets with margarine, and arrange in a grill basket coated with cooking spray. Grill, covered, over medium-hot coals (350° to 400°) for 5 minutes on each side or until fish flakes easily when tested with a fork. Serve fillets with tomato mixture.