Make the yogurt dill sauce first by mixing the yogurt, dill, lemon juice, garlic, salt and pepper together. Refrigerate.
In a jar mix together the olive oil, vinegar, oregano and salt and pepper. Shake well and set aside.
Season pounded out chicken breasts with lemon pepper and grill on a grill pan sprayed with oil heated on medium heat for 4-5 min. aside or until cooked through.
While chicken is cooking toss the veggies in a bowl together with the dressing and the feta.
Serve the salad once the chicken is done with the yogurt dill sauce.