Of all the meat substitutes I've tried over the years, Quorn is the most superior (followed closely by the UK's Asda own brand)
However, this is not available in many countries, only:
United States of America
Australia (which is very frustrating, as I'm living next door in New Zealand and can't get any!)
If you live in any of these countries then check them out as they have loads of products suitable for a BBQ which would result in no extra effort from yourself other than getting them out the packet and sticking them on the barbecue.
Don't forget to keep checking out Veggie BBQ Ideas for more tips for that great vegetarian BBQ