You have to shuck them on the beach. You can't even take any shells to the campground to cook them in. But you can always buy a dozen or more to use the shells to cook the ones you shuck. There are a few places locally to get Oysters. I recommend, Billy The Oyster Guy, across from the Gull gas station/store just before the park, if you're coming from Belfair. $7/doz, any size. He's state licensed, and gives you a receipt. Enjoy!
If you have your fishing license you can read up on shelfish dates an how many you can take. There is grilling spots at the park though.
I believe you have to shuck them there, but you may cook them there as well
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