Cut bell peppers in half lengthwise; discard seeds and membranes. Place pepper halves, skin sides up, on a foil-lined baking sheet; flatten with hand. Broil 12 minutes or until blackened. Place in a zip-top plastic bag; seal. Let stand 15 minutes. Peel and cut into 1/2-inch-wide strips.
Combine the basil and next 6 ingredients (basil through black pepper) in a medium bowl; stir well with a whisk. Add pepper strips; toss well. Let stand 1 hour. Drain peppers, reserving marinade.
Brush both sides of fillets with the reserved marinade. Place fish on a grill rack coated with cooking spray. Grill 5 minutes on each side or until the fish flakes easily when tested with a fork, basting frequently with remaining basil mixture.
Divide pepper mixture evenly among 4 plates. Top each serving with a fillet. Garnish with fresh chives, if desired.