In a bowl, toss greens with olive oil, vinegar, salt and oregano.
Slice Ciabatta rolls and toast them slightly.
Slather 2 tablespoons of hummus on the bottoms of each roll. Top hummus with tomato slices and cucumbers. Divide greens over veggies and top with pepperoncini and olives.
In a small bowl, combine yogurt, garlic, lemon juice and salt. Smear undersides of top roll with yogurt mixture.