Hi @Chris_Keiper ,
As far as I know, such a requirement cannot be achieved through the existing features of MS Flow.
List files action included in the OneDrive connector can only retrieve files under the specified folder and do not include files under subfolders. This has a lot of limitations.
In addition, you could consider using the feature that both OneDrive and Google Drive can synchronize files locally to copy the entire folder.
Sync files from OneDrive to your device, copy the entire folder to Google Drive and then sync to the cloud.
Hope this helps.
Best Regards,