Using a food processor, puree the pickled vegetables, olives, garlic and olive oil into a coarse paste. Season with pepper and set aside.
Slice the bread in half horizontally and remove some of the inside to make room for the filling. Spread the vegetable paste on both cut sides of the loaf. Layer the ham, salami, mortadella and provolone on one half and top with the other half. Wrap the sandwich tightly in foil and refrigerate, weighing it down with a heavy skillet, for at least 1 hour or overnight. Cut into quarters and serve.