Setup people picker to fetch users directly from a OU [USER NOT MEMBER OF ANY SECURITY GP]

Hi All

I would like to know to setup people picker to fetch users directly from a OU. [NOTE: The users are in the OU but not a member of any security group within the OU].

I tried the below setproperty but could not fetch the user in the OU OU_Name. But with the same search base and user filter User Profile import is working absolutely fine.

stsadm -o setproperty -url http://moss2007 -pn peoplepicker-searchadcustomfilter -pv "(&(objectCategory=Person)(objectClass=User)(ou=OU_Name,DC=tailspintoys,DC=com))"

When I try an alternate way by creating a security group GP_Name in the OU and have all the users as members of that goup then with the below setproperty am able to get my expected result:

stsadm -o setproperty -url http://moss2007 -pn peoplepicker-searchadcustomfilter -pv "(&(objectCategory=Person)(objectClass=User)(memberOf=CN=GP_Name,ou=OU_Name,DC=tailspintoys,DC=com))"

Is it something that its must to have a Seurity Group? Do i need to have the Security Group in place for this to work?

Please let me know what should i correct in the setproperty command fetch users from OU.

Regards Ram