Slice the chicken breasts lengthwise along the sides and stuff with Feta cheese. Place chicken breasts into a suitably sized baking pan. Squeeze lemon juice over all chicken then Pour enough olive oil over the chicken to fill the pan to about 1/4 inch. Lightly sprinkle the salt, pepper, oregano, garlic powder, and vinegar over the chicken. Coarsely chop up the olives and sprinkle over the top and inside the chicken. Bake in oven at 325 degrees for 1 hour. Serves up to eight people.