Preheat the oven to 425 degrees.
Combine za’atar in small bowl with 2 tablespoons of olive oil.
Rinse the chicken inside and out. Place the chicken in a large roasting pan. Liberally salt and pepper the inside of the chicken. Stuff the cavity with the lemon slices and garlic. Rub the whole outside of chicken with za’atar olive oil mixture and sprinkle again with salt and pepper. Tie the legs together with kitchen string and tuck the wing tips under the body of the chicken.
Roast the chicken for about 1 hour, or until the juices run clear cut when you cut between a leg and thigh.