Hi Theresa and welcome to the forum!
I'm not experienced with cooking on wooden planks, but I found this link and info at a site that sells planks:
http://www.outdoorgourmet.com/plank-grilling-cooking/frequently-asked-questions.html
Hope this helps,
Chris
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ARE GRILLING PLANKS REUSABLE?
Yes, but we don't recommend it. Technically, if the grilling plank is still in good shape after the initial use it may be reused. Keep in mind that it will take on the flavor of whatever you grilled on it, and some of the essential oils from the wood will be used up from the first round of grilling. If you are grilling something that requires a long cook time, the plank will be too charred to reuse.
Tip: If you cook using the "indirect method" your grilling planks will have the best chance of being reusable. For charcoal grills simply set the coals on one side of the grill and the grilling plank on the other side. Likewise, for gas grills light one side, usually the front, and place the plank on the other (back) side.
If you are planking in the oven, your plank will be in much better condition after use, than if you are planking on the grill.
HOW DO YOU REUSE GRILLING PLANKS?
Clean the used plank by scraping off any food left after the initial use. Rinse in clear running water. Don’t use soap. Re-soak the plank, for 1-8 hours; the longer the better. Use according to recipe.
