Restricting the ability to add outside collaborators to organization repositories
Restricting the ability to add outside collaborators to owners is available with GitHub Enterprise Cloud. For more information, see "GitHub's products."
To protect your organization's data and the number of paid seats used in your organization, you can allow only owners to invite outside collaborators to organization repositories.
You can allow members to invite outside collaborators to repositories or you can restrict outside collaborator invitations to organization owners.
Adding an outside collaborator to a private repository will use one of your organization's paid seats. For more information, see "About per-user pricing."
In the top right corner of GitHub, click your profile photo, then click Your profile.
On the left side of your profile page, under "Organizations", click the icon for your organization.
Under your organization name, click Settings.
In the left sidebar, click Member privileges.
Under "Repository invitations", select Allow members to invite outside collaborators to repositories for this organization.