I always do loads of veggie stuff on the bbbq 
Spring onions, babygem lettuce, cauliflower steaks, tomatoes on the vine can all go straight on the grill once basted with a little oil. Quite often do chopped onions (green or red) in a tray too. Jacket potatoes also. Obviously all of the halloumi too.
If you want to get all showy offy you can make bread on your bbbq which looks pretty impressive.
Sometimes for dessert I’ll slice pineapple, marinade in rum overnight, and grill that up. Delicious.
^This. Game changer indeed. They had them in Aldi for a fiver recently.
My bbbq season tends to only cover March to October. If I had a gas jobby (ie was cheaing) I can imagine I would probably do all year 