Is it possible to Set Field Value for 'Receive (Unmark All)' under Sublist Actions on Item Receipt record?

Yes, you set that under Set up / Accounting / Accounting Preferences, Order Management - there is a section undo Fulfillment to CHECK “Default Items To Zero Received/Fulfilled”. You cannot separate the behavior from fulfillment/receiving.

Thanks for the reply. Yes, I'm aware of this setting but was hoping this could be performed via Workflow as I would like to separate the receiving and fulfilling actions.

You might be able to do that with a workflow action script, might has well just you standard scripting if that is the case.