Your Trigger can select a Specific List in Reminder. Your Action can select a Specific Calendar in Google Calendar. Applet describe it , " Fin!! {{TITLE}} ".
If
Reminder completed in list
This Trigger fires every time a new reminder is completed in a list you specify.
Then
Quick add event
This Action will add an event to your Google Calendar. Simply include a detailed description of when and what.
Explore more great ways to automate Google Calendar and iOS Reminders