Couple of options: The standard organic answer to grubs is nematodes. Organic suppliers typically carry them. They are expensive, and if you use them, you'd better makes sure everything goes exactly according to directions (for instance, soil moisture and temperature need to be just right) or they may not work well. But if all goes well, they can do the trick.
Another option is diatomaceous earth. I"m not crazy about it in lawns, but in a vegetable garden situation, you can till some in into the top few inches of soil and it might work pretty well.
Lastly, milky spore works well on Japanese beetle grubs, but ONLY japanese beetle grubs. So if you know that that's what you primarily have, then it's a good option. OTherwise, it's useless.
So, take your pick. Personally, I would try the diatomaceous earth first. But keep in mind that a moderate number of grubs won't hurt your veggie garden too much. If they're really thick, then control measures are warranted. But if you're digging in your garden and just see a few here and there, you can safely ignore them.