SharePoint Add Gropup to Site using Power Shell

Simple Script to add an existing group to a site or sites.

$sites = Get-SPWeb "Site url"
foreach ($site in $sites.webs)
{
$site.AssociatedGroups.Add($site.SiteGroups["Group Name"]);
$GroupAccount = $site.SiteGroups["Group Name"]
$timeoffassignment = New-Object Microsoft.SharePoint.SPRoleAssignment($GroupAccount)
$timeoffrole = $site.RoleDefinitions["Read"]
$timeoffassignment.RoleDefinitionBindings.Add($timeoffrole)
$site.RoleAssignments.Add($timeoffassignment)
$site.Update()
$site.Dispose()
}