Summary: Use a single line Windows PowerShell command to list all users in an OU.
How can I list all users in a particular organizational unit (OU)?
Use the Get-ADUser cmdlet from the ActiveDirectory Module (available from the RSAT tools). Specify the SearchBase as the name of the OU, and use a wildcard pattern for the Filter.
Get-ADUser -Filter * -SearchBase "ou=testou,dc=iammred,dc=net"
Note In Windows PowerShell 3.0, you do not have to load a module prior to using it.