In order to maximize time and participation from everyone involved, it’s a good idea to provide a combination of peer feedback and teacher feedback. Give learners the chance to review each others’ work before stepping in and offer extra points for those who contribute more to the peer-review process. It’s well worth investing some time in learner training and in how to give constructive peer feedback if it’s the first time your learners have worked in this way.
Assess the process, not just the final product. Assess the sub-tasks or tasks at different stages, assess both individual students’ work and also give a grade for group work at the end of the process.
Provide formative feedback during the process. This can include ideas on how to improve drafts, feedback on early stages of the project, feedback on brainstorming and picking topics, or comments about the outline or structure of the project.
Assess the ability of the group to adjust to the task requirements (in terms of steps or subtasks, the processes followed).
Feedback on the formal linguistic aspects can become secondary during the group work process. Provide feedback on linguistic aspects only when necessary.
Have learners reflect on the collaborative process and group work as a final step or as a post-task and include that as an evidence of group work, with the possibility of assessing that evidence at the end.
Use a screencasting tool to provide feedback by having teachers provide audio comments on written projects or replay students’ video projects and stop wherever necessary to provide comments. This results in a new video clip with feedback which can then be sent to students. Here’s a video of Russel Stannard on using screencast to give feedback which can provide some ideas: