Considerable efforts are needed to construct a virtual environment for Military Operations on Urbanized Terrain (MOUT). The models of various objects used in one application are often specifically designed for that application, thus are not generally suitable for other applications. We often have to rebuild many object models for a new simulation setup, which is very tedious and time consuming. To reduce the cost and time in building up different simulation environments, it is therefore highly desirable to have a repository of object models that are interoperable and extensible thus can be reused in different applications. To this end, we propose a generic model framework which supports model interoperability and reusability for MOUT simulations. Our experiences with Twilight City, a virtual training environment for MOUT, show that the proposed framework is successful in creating a repository of models for various simulation setups.