Using a large ziptop bag, add all of the ingredients; turn several times to ensure chicken is well coated.
Refrigerate for at least 3 hours or overnight.
Preheat grill to medium-high (~375°F) heat.
Remove chicken from marinade; discard excess marinade.
Grill chicken for 10-12 minutes, turning occasionally, or until fully cooked.
Let chicken rest for 5 minutes before slicing.
For the Yogurt Sauce
Using a medium bowl, whisk all of the ingredients together. Cover and refrigerate until needed. (Tip: This yogurt sauce will taste better if you make it a day ahead of time and refrigerate it overnight!)
For the Wraps
Assemble the wraps by spreading several tablespoons of hummus on top of each flatbread.
Top with lettuce and sliced grilled chicken.
Add cucumbers, tomatoes, red onion and feta cheese. Drizzle top with yogurt sauce.