How to Make It
In a food processor, combine the sun-dried tomatoes with the olives and oregano. Season with pepper and process to a coarse paste.
Lightly brush 1 side of each slice of bread with olive oil and set on a large baking sheet, oiled side down. Top half of the bread with the provolone, spread each slice with 1 tablespoon of the tomato-olive pesto and top with the mozzarella. Close the sandwiches with the remaining bread, oiled side up.
Heat a griddle or a very large skillet. Arrange 3 or 4 sandwiches on the griddle and top with a cast-iron skillet: do not press the pan down. Cook the sandwiches over moderately high heat until golden on the bottom, about 2 minutes. Flip the sandwiches and cook until browned and the cheese is melted, about 2 minutes longer. Transfer to a wire rack to cool. Repeat with the remaining sandwiches.
Cut the crusts off the sandwiches, then cut into triangles and serve.
For an even more flavorful sandwich, brush the bread with the oil from the jar of sundried tomatoes. Strain the oil first through a sieve to remove any small bits that would burn on the griddle.