In a real-time distributed computing environment, security is critical to protect the system from unauthorized access especially since such systems are being used in time critical applications. Access Control mechanisms have been introduced during the last several decades and have offered a basic and powerful means for enforcing security. In this paper, we examine the concepts of the TMO (Time Triggered Message Triggered Object) scheme that provides guaranteed real-time services in a distributed object computing environment. We also examine access control mechanisms; such as the traditional model, the RBAC (Role-based Access Control) model and the UCON (Usage Control) model. The main contribution of this paper is applying the traditional, RBAC and UCON models to the TMO scheme in order to provide a secure real-time distributed environment.