Slice the Italian bread in half horizontally and hollow out some of the soft bread from the inside to create space for the fillings.
In a small bowl, mix the olive oil, red wine vinegar, dried oregano, salt, and pepper to create a dressing.
Brush the inside of both halves of the bread with the dressing.
Layer the mortadella, salami, provolone cheese, and ham evenly on the bottom half of the bread.
Spoon the olive salad generously over the meats and cheese.
Place the top half of the bread on the sandwich and press down gently.
Wrap the sandwich tightly in plastic wrap and refrigerate for at least 30 minutes to allow the flavors to meld.
Before serving, slice the sandwich into wedges and enjoy.