Can i put mussles and oysters together on a tray

Hi Donna, Yes you can, but cook the mussels like ChefJune says. If you give us more details we can give you better advice.

How are you preparing the mussels? the oysters? Mussels are not ordinarily served raw.
Raw fish should always be served on ice.

Raw? Absolutely! Google "seafood towers" for inspiration! ;-)