Source: Some show I watched years ago and my own experimentation
Cut eggplant with skins on about 2 inches thick - judge your total amount of eggplant for yourselves.
Put in lidded container with splash of balsamic vinegar
Shake until most of the vinegar is absorbed
Put in some oil (anywhere from a tablespoon per eggplant up)
Sprinkle oregano, basil, and pepper on eggplant
Shake until spices are evenly distributed - apply more before putting on grill if neccessary.
Grill eggplant on hot grill/bbq until nicely browned scores appear - turn and grill other side. Eggplant should be softened, but not soggy.
Will also work on George Foreman grill - slightly soggier than BBQ result
Tastes better if eaten relatively warm.