1. Heat grill pan. Brush sausages with 1 tablespoon oil; cover and cook 5 minutes per side. Reduce heat; cook 3 minutes, until cooked through. Cover and keep warm.
2. Meanwhile, heat 1 tablespoon oil in a large skillet over medium heat. Add peppers; cover and cook, 5 to 8 minutes, until softened. Stir in onion, 1 tablespoon vinegar, garlic, 1 teaspoon oregano, and salt. Cover and cook until vegetables are golden brown, 5 minutes.
3. Combine remaining 3 tablespoons oil, 2 tablespoons vinegar, and 1 tablespoon oregano; brush on bread. Fill with sausages and peppers. Makes 4 servings.