I'd say so, brush with oil and give them a short blast, no reason they shouldn't be fine, might work better however to put them on there "en papilotte" (foil envelope in this case) with some seasonings.
Tin foil, it really is a essential tool for cooking most fish on a barbie. Gut, de-head the dab, cover in oil and possibly some crushed garlic and some fresh herbs, wrap it in foil and put it on the barbie for a a few minutes. the flesh will literally fall off the fish, and it will be well nice. This method can be done for pretty much any fish you want to try and cook on the barbie.
If you just brush the fish with oil and place it on the barbie bare it will probably blacken and although still taste ok will not be as nice.