Whisk the olive oil, lemon juice, lemon zest, oregano, garlic, salt and black pepper and coat the chicken with half of the mixture for 30 minutes in the refrigerator.
Stir the yogurt into the remaining lemon-herb mixture and chill the sauce.
Heat a grill or grill pan to medium-high and oil the grates lightly.
Grill the chicken for 4 to 6 minutes per side, turning once, until marked and 165°F at the thickest point.
Rest the chicken for 5 minutes and toast the ciabatta cut-side down on the grill for 1 minute.
Spread each roll with lemon-herb yogurt and assemble with 1 lettuce leaf, 1 chicken cutlet and 1 tomato slice.