Updating Project/Task Owning Org

We need to update the org on many projects.  We tested it and the simple update worked at project level.  But tasks were not updated.  Is there a simple method to update all the tasks on a project at the same time?  Some projects have many tasks.  Doing this manually will be very time consuming.  Or is there a mass adjust function that can update the project and tasks all at once? We are on 11.5.10.