Not sure if I have understood your question correctly or not, but I have used Forum to do something similar, but not identical, to what I think you are asking. I made 4 different text files available and then set up 4 separate topics in forum (I allocated my class into 4 groups). I then got each member of the group to do their summary of the text and post to their topic. The group then agreed an edited best version and sent that. My aim was not to assess them but for each group to construct a resource that all the class could then use in an assignment. At the end of the exercise there were 4 resources for all to use. My method probably wasn't the most elegant and I'd welcome any ideas for how to do it better, but in the end it did work!