There has been a growing trend toward collaborative environments especially those utilizing browser-based interfaces which can be seen in modeling tools such as AToMPM and WebGME. In response to the growing interest in collaborative modeling, we explored existing systems and potential solutions to identify the various features relevant to collaborative modeling systems. In this paper, we detail the feature diagram resulting from our exploration of collaborative modeling systems. We also detail the features of an existing collaborative system both to illustrate the use of the diagram and further explore the features. Through this feature diagram we identify key areas for collaborative modeling systems. We hope the feature diagram will be used to guide development, analysis, and discussion around collaborative modeling systems.