Fish suitable for grilling are trout, whitefish, bluefish, snapper, or mackerel.
(In Greece, the fish are usually served with their heads and tails intact.
You may prefer to remove the heads at least, because some people are revolted by a whole fish on their plate.
However you decide to serve the fish, allow 1 pound for each person.) Heat charcoal until white.
Arrange grill so that it is about 4 inches from coals.
Use a hinged basket grill for easier turning; oil it well to prevent fish from sticking.
Combine olive oil, lemon juice, oregano, salt, and pepper.
Brush fish generously with mixture.
Place in basket grill.
Cook on one side about 7 minutes.
Turn over and cook an additional 7 minutes.
Serve fish with remaining sauce.