I remember this being SO simple:
Create a NET LOCALGROUP .bat/.cmd script
NET LOCALGROUP Administrators groupname "ServerAdmins" /ADD
2) In Group Policy Management select the OU where you want the GPO to be applied
3) Create "...new GPO and Link it here..." named <AddSrvAdmToLocal>
4) Edit this GPO by modifying the Computer Config | Policies | Windows Settings | Scripts Item
5) Open the Startup script object in the right pane and click add to choose the script to run when the computer starts up.
6) Close editor and add impacted devices under the Scope tab of the GPO (e.g. - Domain Computers)
a. in this case I have specifically chosen a couple of non-production servers and added those.
Doing Group Policy Modeling shows the GPO as being applied.
However, when I reboot the two servers nothing happens. The group does not get added.
Something in the back of my mind tells me that I am missing something but I can't for the life of me think of what it might be.