Quite honestly, pit beef is usually top round, brisket, or bottom round chunks that are pre-marinated in some form of spice. (Mostly dry rubs.) They are then cooked ie: flipped, rotates and turned with tongs over top a barbie in a way that sears in the flavor on all sides. Generally speaking you can have a large chunk just lightly crispy on the outside and perfectly medium rare on the inside that is moist and tender and melt in your mouth. Some people like their beef well done, and that is fine too--the key again is to get the inside to have it's moistness and not taste like cardboard.
Most of these meats are cooked on a wood charcoal pit, propane pits, or hardwood open style pit. The pits mixed with the dry rub marinades really seal in the flavor. The outcome is a lightly smoked meat (which can have more or less flavor based on the type of woods you may be using to cook it) mixed with moist goodness. The meat is supposed to melt in your mouth as it is sliced thin.
Baltimore eats it on a large kaiser roll with thinly sliced onions and horsey sauce. I have seen a lot of people put horseradish, mayo, and bbq sauce on it but honestly a mayo-horsey blend is the original way to eat it.
Mistakes oven occur when
- the meat is sliced too thick
- the meat is dried out
- the meat is sliced the wrong away against the grain and it's hard to chew
- it's not marinated
- it's cooked in an oven (that's cheating.)