Rub 4 halved red bell peppers with olive oil. Grill, turning, until tender, 15 minutes. Transfer to a bowl, cover and let steam 10 minutes; peel off the skin. Whisk 3 tablespoons olive oil, 2 tablespoons each red wine vinegar, chopped scallions and parsley, 1 teaspoon finely chopped oregano and 1/2 teaspoon salt. Drizzle over the peppers.