Get the bottom level branches of an Active Directory Organizational Unit

Get-OrganizationalUnitBranches.ps1

function Get-OrganizationalUnitBranches(
  [Microsoft.ActiveDirectory.Management.ADOrganizationalUnit]
  $OrganizationalUnit
) {
  [array]$Collection = @()

  $Children = Get-ADOrganizationalUnit `
    -Filter * `
    -SearchBase $OrganizationalUnit.DistinguishedName `
    -SearchScope OneLevel 

  if (!$Children) {
    return $OrganizationalUnit
  }

  foreach ($Child in $Children) {
    $Collection += Get-OrganizationalUnitBranches -OrganizationalUnit $Child
  }

  return $Collection
}

Get-OrganizationalUnitBranches -OrganizationalUnit (Get-ADOrganizationalUnit -Identity $RootOuDistinguishedName)