Organization owners, and members with admin privileges for a repository, can invite outside collaborators to work on the repository. You can also restrict outside collaborator invite permissions to only organization owners.
- In the top right corner of GitHub Enterprise, 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.

- Click Save.