Calendar Appointments into Google

Q: A customer receives an Outlook Calendar appointment from a co-worker.  They want to accept it on their calendar but also have it show up on their Google Calendar.  They don't want automation or any syncing applications.  They have tried:

1. forwarding the message from non-microsoft webmail to their gmail address - fail.
2. forwarding the message from their iphone (with the visible ics attachment) to their gmail address - fail.

A: Open the invite in Outlook, forward it to your gmail address, then accept it in Outlook.