Set a startup script in group policy with the following line:
NET localgroup Administrators /add “domain_name\domain_group”
Once your computer is joined to the domain, place the computer in the proper OU (where your startup script lies) and reboot. (Or preconfigure your ADUC with the computername in the proper OU)
More things you can do with scripts are suggested here:
Bad Behavior has blocked 149 access attempts in the last 7 days.