Adding Security groups in SharePoint and Office 365 groups

trenish - The site members won't carry over into my provisioning template, presumably since that is basically managed as a Group resource.  I understand that this can be achieved in a 'tenant template' which I haven't yet mastered.  Or the preferred method of building an Azure Package which is a bit beyond my pay grade but also the client would require additional licensing. However, I've been able to craft two serviceable powershell methods.  One for my initial setup as I build sites and the other for future new hires to all existing sites:

1. Add a list of employees as 'Site Members' to a M365 Group

2. Add a new hire to a list of M365 Groups

Both processes worked for me.  They require exchange admin and a connect to exchange via powershell.  I believe you need a cmdlet installed first and local admin rights to the machine.

Connect-ExchangeOnline -UserPrincipalName you@email.com -ShowProgress $true

#Add multiple users to a single group.  Replace path and file name for your CSV and the O365 group name.  CSV header should be a single column with a header of 'Member' without quotes

Import-CSV "C:\path\members.csv" | ForEach-Object {
Add-UnifiedGroupLinks –Identity "O365GroupName" –LinkType Members  –Links $_.member
}

#Add single users to list of groups.  Replace path and file name of the TXT and the email

Foreach ($group in (get-content "c:\path\groups.txt")){
    Add-UnifiedGroupLinks $group –LinkType Member -Links "newhire@email.com"
}