Wash and dry lettuce leaves; stack and slice or tear into sandwich-sized pieces. Slice tomatoes into 1/4-inch rounds and place on paper towels to drain briefly. Peel and thinly slice the red onion into rings. If using pickles or pepperoncini, slice them thinly. Set all prepared vegetables aside on a tray.

Make dressing/spread

In a medium bowl, combine mayonnaise (1.5 cups), Dijon mustard (6 tsp), olive oil (2 tbs), red wine vinegar (2 tbs), dried oregano (2 tsp), garlic powder (1 tsp), salt (1 tsp) and black pepper (1 tsp). Whisk until smooth. Taste and add crushed red pepper flakes (up to 1 tsp) if you want heat. This yields a creamy tangy spread for all 6 subs.

Prepare bread

If rolls are whole loaves, slice each lengthwise about three-quarters through so they hinge open. Lightly brush the cut interior of each roll with the remaining 2 tbs olive oil. (Optional) Place rolls cut-side-up on a sheet pan and lightly toast in a 375°F / 190°C oven for 4–6 minutes until just golden and slightly crisp to help hold fillings and prevent sogginess.

Assemble turkey and cheese layers

Open each roll and spread an even layer of prepared mayonnaise-mustard dressing along the bottom and top interior surfaces (about 1/4 cup spread per 1-ft sandwich). Layer 1 cup of sliced roasted turkey breast per sandwich (approx. 6 cups total divided evenly), arranging slices so they overlap across the length. Top the turkey with three slices of provolone cheese per sandwich (18 slices total).

Add vegetables and season

On top of the cheese (or under the cheese if you prefer cheese closer to bread), distribute lettuce (about 1 cup per sandwich), 1 tomato per sandwich (sliced), and red onion rings evenly among the 6 sandwiches. Add pickle chips or pepperoncini as desired (2 pickles/peppers per sandwich if using). Sprinkle a light pinch of salt and a grind of black pepper across each sandwich to taste.

Finish and portion

Close each sandwich, press gently to compact the fillings, and if desired, wrap tightly in parchment or foil and let rest for 5–10 minutes to let flavors meld. For service, slice each 1-ft sub into portions or leave whole. Cut each sub into 12–18 pieces if serving as party tray (optional).

Storage and make-ahead

If making ahead more than 2 hours, store the dressing separately and keep vegetables in airtight containers. Assemble up to 1 hour ahead, wrap tightly, and refrigerate. Consume within 24 hours for best texture. Do not freeze assembled sandwiches.