To make the herb sauce; combine all the ingredients into a small bowl, stir well and set aside.
Slice the capsicums into chunky pieces, remove the seeds and place in a bowl. Drizzle over with olive oil and toss to coat.
Slice the chicken breast in half and butterfly it open. Drizzle over olive oil and sprinkle the Za’atar spice mix.
Heat a BBQ grill to medium-high heat or a heavy base grill pan. Add the capsicum and chicken. Turn the capsicums once they start to blister and lightly char. Once they become soft, remove them from the grill and set them aside. Turn the chicken once light golden char marks develop, then remove from the heat once the other side is lightly golden.
To build the wrap, add a handful of baby spinach, followed by the grilled capsicum, the chicken breast sliced up into strips followed by the avocado sliced into thin slices. Spoon over a good dollop of the herb sauce. Roll up the wrap and place it back on the BBQ grill until lightly heated. Serve straight away.