The ultimate summer sandwich! It brings together a fair blend of superior Italian flavors including a bakery fresh ciabatta bun, balsamic marinated chicken breast, fresh mozzarella and tomatoes, plus an intensely herby pesto. You'll want this one on repeat!
To a gallon size resealable bag add olive oil, white balsamic vinegar, oregano, salt and pepper. Shake to evenly distribute ingredients then place chicken in bag with marinade.
Seal bag while pressing air out then rub marinade over chicken. Transfer to fridge and let rest at least 30 minutes but no longer than 4 hours.
To prepare sandwiches and grill chicken, preheat a gas grill over medium-high heat (400 to 425 °F).
Brush grill grates lightly with oil then grill chicken (with lid closed) until charred on bottom, about 4 to 6 minutes. Turn chicken then top with mozzarella slices and continue to cook chicken through, about 4 minutes longer (it should register 165 °F internally). Transfer to a plate and cover with foil, rest 5 minutes.
Meanwhile spray rolls on split side with olive oil cooking spray then place rolls on grill cut side down. Grill until lightly toasted about 1 minute (you can also grill on opposite side if preferred).
To assemble sandwiches spread pesto on split side of lower halves of the rolls. Layer the arugula over the bottom halves, top each with a chicken breast with the cheese side up, layer on tomatoes.
Spread remaining pesto over cut side of top halves of the rolls then turn and press over sandwich. Serve right away.