How long ? It depends on your food choice.
Chicken – an hour to two hours at 120 C.
Rack of ribs will take from 2 hours to 4 hours 30 minutes at 115 C.
A boneless beef or pork joint can take as long as 6 hours at 115 C.
Vegetables – 90 minutes to 2 hours at 95 – 105 C
Seafood – 35 to 45 minutes at 100 – 105 C
If you are using barbecue sauce wait to brush it on until the final 30-45 minutes of cooking. You do not want it to burn, and because most barbecue sauces have a lot of sugar in them, they will burn easily. When barbecuing fish, do not sauce until the last 15 minutes. You will be able to spot that the meat is ready with some visual cues. Meat on bones will begin to pull away.
When you turn or rotate meat it will begin to fall off the bone. The flakes on fish will separate easily. The interior of a beef or pork will be somewhere around 70 C – this is the only meat that should be barbecued or smoked with a meat thermometer. What happens if your heat was just too high and things are looking charred? Well, hopefully you did not let it go this far because you’d been checking every hour to 90 minutes.
But if it looks like you have too much char and the meat is not yet done, have no fear: Finish the meat in a 120 C oven. You will still have enough smoky taste to impress your guests. Once your meat is done, remove it to a platter, add more sauce and let it rest for 10-15 minutes. Let a big meat joint rest for 20-25 minutes. Add even more sauce right at service and enjoy! You’ll know you cooked real barbecue if everyone has sauce under their fingernails…