The time-triggered message-triggered object (TMO) structuring scheme has been established to remove the limitation of conventional object structuring techniques in developing applications containing real-time (RT) distributed computing components. It is a natural and syntactically small but semantically powerful extension of the object oriented (OO) design and implementation techniques which allows the system designer to abstractly and yet accurately specify timing characteristics of data and function components of high-level distributed computing objects. It is a unified approach for design and implementation of both RT and non-RT distributed applications. A cost-effective way to support TMO-structured distributed RT programming is to build a TMO execution engine as a middleware running on well established commercial software/hardware platforms. In this paper, we present an efficient middleware architecture named TMO Support Middleware (TMOSM) which can be easily adapted to many commercial-off-the-shelf (COTS) platforms. The performance of a prototype implementation of TMOSM running on Windows NT platforms is also discussed.