I parboil some potatoes, cut them into small chunks, shove them in to a plastic bag and pour in some olive oil, finely chopped garlic and chopped fresh rosemary. Shake the spuds until they are all covered with oil, garlic and rosemary. Bit of salt and pepper, too. Then roast in the oven to serve with your barbecue. We often do a coleslaw, a tomato salsa dip, a bowl of warm barbecue sauce and halved roasted red peppers with two tomato quarters, anchovy, garlic and a basil leaf inthe cavity (Delia Smith recipe for Piedmont roast peppers). Sometimes do a yogurt and cucumber raita as a sauce, so delicious and very cooling. We sometimes do a butterflied leg of lamb on the barbie, that's great to just pick off the meat.
For starters, we often do 3 or 4 different dips plus crudites, or a gazpacho soup. Not too much starters, though as there's usually so much food for the mains. Dessert in our house is usually light, am doing almond madeleines and poached apricots for our barbecue in a few weeks time, and a pavlova for the one after that. We also sometimes barbecue sticks of fresh pineapple on the barbecue, When the fruit sugars caramelise, they are delicious! Hope this is helpful.