Combine all the marinade ingredients then add the chicken and coat the chicken in the marinade. Cover and allow to marinade for at least 30 minutes but up to 24 hours in the fridge.
Make the tzatziki according to recipe instructions.
Cook the chicken in a hot pan/griddle pan until golden brown on both sides and cooked through. Remove from the heat and allow to rest for 5 minutes before slicing.
Serve the grilled chicken with the tzatziki, lettuce, tomato and onion in a warmed wrap.