The most common meat barbecued in Poland is sausage, one of the medium thickness kind (aroung an inch in diameter) and not the "dry" type (lean meat gets dry, a bit of grease is essential for proper cooking) usually cut in some kind of pattern to allow fat drop as it melts. Often seasoned with herbs, pepper ect. (no salt though, agree). Served with fresh (or bbq toasted) crunchy Polish bread, mustard, ketchup, veg of some kind (cucumbers, tomatoes, mixed veg salad, anything) and often beer or wine.
Tired of the same old sausage, Poles now barbecue all sorts of meat, often pre-marinated in vinegar-seasoning mixture. Whatever is too soft (e.g. fish) is packed in aluminium foil. Polishness demonstrates itself in salads, spices used and serving customs, after all how many sorts of meat can there be?
Often instead of a typical grill or bbq (which have been popular only recently) Polish organize a fire. Then you can bury potatoes in hot ashes, roast a sausage held on a long stick (making sure it doesn't break and fall into the fire), or make quick toasts using hte same method. Unlike with the bbq, you can stay late into the night, warming up your hands and feet by the fire, playing the guitar and enjoying the atmosphere its light creates. I guess that's the most Polish thing of all.