I'm an administrator for a group. The group is made of people both inside and outside of my organization. I've got the settings designed so that all group members can contribute content to the group:

However, people at the group member level are not able to contribute content. They do not see the option when logged into the group. I'm not sure how to fix this. People do not need to be able to edit each other's content, but do need to be able to contribute their own content to the group.