Souvlaki Marinade:
3/4 cup balsamic vinaigrette salad dressing
3 tablespoons lemon juice
1 tablespoon dried oregano
1/2 teaspoon freshly ground black pepper

4 skinless, boneless chicken breast halves

Tzatziki Sauce (cucumber sauce):
1/2 cup seeded, shredded cucumber
1 teaspoon kosher salt
1 cup plain yogurt
1/4 cup sour cream
1 tablespoon lemon juice
1/2 tablespoon rice vinegar
1 teaspoon olive oil
1 clove garlic, minced
1 tablespoon chopped fresh dill
1/2 teaspoon Greek seasoning
kosher salt to taste
freshly ground black pepper to taste

4 large pita bread rounds
1 heart of romaine lettuce, cut into 1/4 inch slices
1 red onion, thinly sliced
1 tomato, halved and sliced
1/2 cup kalamata olives
1/2 cup pepperoncini
1 cup crumbled feta cheese