To get a list of members of an AD security group using PowerShell, run the following from the Active Directory Module for Windows PowerShell.

Get-ADGroupMember “<GroupName>” | Select Name, SamAccountName, objectClass

Or, to get a list of user ojectClasses only, run:

Get-ADGroupMember “<GroupName>” | where {$_.objectclass-eq “user”} | Select Name, SamAccountName

Similar, to get a list of group ojectClasses only, run:

Get-ADGroupMember “<GroupName>” | where {$_.objectclass-eq “group”} | Select Name, SamAccountName