Place the chicken in a large bowl with the oregano, lemon juice, 2 tablespoons of the olive oil and the salt. Season with cracked black pepper and toss well to coat. Set aside to marinate for 15 minutes.
Heat 1 tablespoon of olive oil in a large frying pan over medium heat. Cook the chicken for 6-8 minutes, stirring occasionally, until golden and cooked through. Remove from the pan and set aside.
Add remaining oil to the frying pan and cook the rye bread pieces for 4-5 minutes until golden and crisp.
Grate 1 tomato into a large serving bowl, discarding the skin. Roughly chop the remaining tomato and add it to a large bowl along with the avocado, feta, olives, cooked chicken and toasted rye bread.
To make the dressing, whisk together the olive oil, lemon juice, salt and pepper. Pour the dressing over the salad and gently toss to combine and serve.
4 servings