Add a Group Policy in:
Computer Configuration, Windows Settings, Scripts (Startup/Shutdown) -> Startup and apply to the appropriate OU’s.
Add a batch file here with the following content (example):
NET LOCALGROUP Administrators /ADD “DOMAINNAME\Domain Admins”
NET LOCALGROUP Administrators /ADD “DOMAINNAME\Group_IT”
Now you can simply add the necessary users in “DOMAINNAME\Group_IT”, and they will have local administrator rights on the PC’s in the selected OU’s.