Sherry vinegar adds a distinct savory flavor to sweet peppers that pairs well with smoked ham. These sandwiches are quite portable when wrapped tightly, so consider packing them in your lunch box for work or a picnic. Pack a few potato chips to eat along with the sandwiches, if you like.
In a small bowl, whisk together vinegar, garlic, mustard, oregano, salt and pepper until well combined. Stir in peppers and onions and toss to coat. Cover and refrigerate for 15 minutes, or preferably overnight. Layer rolls with provolone, cheddar, ham and lettuce, then top with marinated peppers and onions and drizzle with a bit of the marinade, if you like. Cut sandwiches in half crosswise, transfer to plates and serve.