[active-directory] LDAP root query syntax to search more than one specific OU

I don't think this is possible with AD. The distinguishedName attribute is the only thing I know of that contains the OU piece on which you're trying to search, so you'd need a wildcard to get results for objects under those OUs. Unfortunately, the wildcard character isn't supported on DNs.

If at all possible, I'd really look at doing this in 2 queries using OU=Staff... and OU=Vendors... as the base DNs.