Crumble the bread in a food processor.
Chop finely the onion, add the oregano, thyme, mint and the parsley to it.
Add some garlic powder. Now add the egg.
Add all this to the beef (previously seasoned with salt and pepper), mix all this until well blended.
Let it rest for around 30 minutes. Cut the feta in stripes.
Divide the ground beef in four portions and shape them into balls.
Flatten them, put a slice of feta on one half and fold the other half over it, seal the edge good.
Preheat the grill and brush it with a little of olive oil.
Bake them on the grill just until cooked on the outside.
In a oven previously preheated at 200 degrees celcius bake the Bifteki for around 30 minutes.
Serve them with your favorite salad, with feta, cucumber and olives.