Preheat oven to 400 degrees. Grease a small baking dish with butter.
In a small bowl, stir together marjoram, rosemary, thyme, pepper, cumin and za’atar. Rub chicken breasts with spice mixture.
Place chicken breasts in baking dish and bake for 10 to 15 minutes until cooked through. Rest chicken 10 minutes before cutting into bite-size people.
In a small bowl, whisk together ingredients for the sauce. Set aside.
Cut the top off of each pita to form a large pita pocket. Loaded up the pita with chicken, cucumber, tomato, sliced onion, pita chips, and feta. Top with the sauce and sprinkle a little extra marjoram on top. Serve.