Grill peppers on medium-high, turning once, until soft and charred in spots, about 5 minutes per side.
When cool enough to handle, peel the skins.
Discard the skins and slice the peppers into thin strips.
Place the bell peppers, black olives, parsley, garlic, green onion, olive oil, and vinegar into a salad bowl.
Add salt and black pepper to taste.
Mix ingredients well, cover and marinate 2-3 hours. Stir the mixture once or twice.
Serve at room temperature or chilled.