Webbers are the best for this if you have one,(Unless you can cook it in among some ashes!!!) gill gut your Red and with a sharp knife stab some pockets at variouse sections of the side of the fish or just make some cuts and fill these with a dash of butter and a clove of garlic to each cut/pocket..salt pepper rubbed on the fish itself , stuff the stomache with carrots, cellery or whatever takes your fancy...
Get a cup and halfe fill it with Olive Oil, near halfe with squeezed lemon juice, handfull of Rubbed/crushed oregano leaf and stir till it goes like emulsified oil..
Brush on the outside (Both sides) of your red emperor, wrap in foil and lay in the webber remembering to turn halfeway through cooking..Whats left of the basting mixture you can leave till the fish is ready to be served ..tastes a treat...as for time??depending on size of the beast anywhere from hour n a halfe to two hours....