Office 365 Add User to Teams in Bulk in Powershell

Create a CSV file with the following columns.

User Powershell to import CSV file using Teams module.

Install-Module -Name MicrosoftTeams -Force

Connect-MicrosoftTeams

$users = import-csv "C:\path\to\csv\teams.csv"
Foreach($user in $users)
{
    Add-TeamUser -GroupId $user.GroupID -User $user.User -Role $user.Role
}