Preheat oven to 375F/190C.
Trim four large chicken breasts, removing any fatty or undesirable parts. Rub chicken on both sides with Greek Seasoning (affiliate link).
Heat olive oil in frying pan over medium high heat, then add chicken breasts and cook about 2 minutes on first side, until it's starting to barely brown.
Turn chicken over and cook a few minutes on the other side. (Don't cook too long at this point or the chicken will be overdone by the time it bakes.)
Remove chicken to cutting board and let cool a minute or two until it's cool enough to handle.
While chicken cooks and is cooling, drain olives and slice, slice tomatoes in half, removed seeds from peperoncini and slice, and crumble the Feta.
Then cut each chicken breast lengthwise into 3-4 strips.
Spray an 8"x13" or 9"x12" casserole dish with non-stick spray and arrange chicken breasts going crosswise in the dish.
Sprinkle tomatoes, olives, and peperoncini over the chicken strips and crumble Feta over the top.
Season to taste with fresh-ground black pepper.
Bake 25 minutes or until chicken is hot and cheese is starting to melt.
