Whisk the eggs with the oregano in a mixing bowl. Add half of the feta.
Heat the oil in a non-stick frying pan and pour in the eggs. Let the mixture spread out.
When the surface of the omelette has almost set, add the chopped seafood, pepper and olives, then scatter the remaining feta on top.
Cook for 3 minutes, then add the parsley and fold the omelette in half.
Cook for another minute or so, then turn over, cook for a few second.
Using a spatula, remove the omelette to a plate, cut it in half and serve.