Spread the mayo on the bottom half of the loaf of bread.
Layer slices of ham, capicola, salami, mortadella, and prosciutto. Top with slices of the provolone cheese. Top with slices of tomatoes and season with salt and pepper. Add the onions and lettuce over the top.
In a small bowl whisk together the oil, vinegar and oregano until emulsified. Drizzle over the sub. Add pepperoncini peppers (if using).
Close the sandwich and cut into 4 equal sections. Serve immediately.