In a large bowl, whisk together red wine vinegar, olive oil, oregano, garlic powder, salt, and pepper to make the dressing.
Add diced salami, pepperoni, and provolone cheese to the bowl with dressing.
Add cherry tomatoes, red onion, olives, and pepperoncini. Toss to combine.
Add chopped iceberg and romaine lettuce, tossing everything together until well coated with dressing.
Hollow out some of the bread interior from both halves to create space for filling.
Pile the chopped salad mixture onto the bottom half of the bread.
Top with the other bread half and press down gently.
Cut into individual portions and serve immediately.