The success of groupware software largely depends on its capability for being reused in different collaborative scenarios without requiring significant software development efforts or user technical involvement. During the last decade several toolkits, frameworks, and specialized middleware software layers have been proposed as potential solutions to the groupware reusability problem. Those solutions cover common groupware functionality such as group formation and management, group awareness, shared workspace management, etc. This paper is focused on the reusable support to one of these common functionalities: the so-called object-level coordination that deals with multiple participants? sequential or simultaneous access to the same set of shared objects in a collaborative setting. The paper compares existing object-level coordination proposals and analyzes their capabilities and level of reuse. Starting from that analysis, and using a bottom-up approach, the paper also proposes a high-level reference model that identifies the desirable set of required functional elements, as well as their relationships, that reusable object-level coordination support should contain. The purpose of this reference model is twofold: to be used as a comparison framework for analyzing existing or yet-to-come object-level coordination building blocks; and, to be used as a starting point for developing new object-level coordination solutions (or redesigning existing ones) satisfying the whole set of requirements implicitly collected in the model. In addition to detailing the proposed reference model, the paper also illustrates and discusses both potential ways of using it.