Grant all department members the required IAM permissions for their respective projects.

Create a Google Group per department and add all department members to their respective groups. Create a folder per department and grant the respective group the required IAM permissions at the folder level. Add the projects under the respective folders.

Create a folder per department and grant the respective members of the department the required IAM permissions at the folder level. Structure all projects for each department under the respective folders.

Create a Google Group per department and add all department members to their respective groups. Grant each group the required IAM permissions for their respective projects.