Object-based programming techniques help to reduce the cost of software development and maintenance due to the benefits of reuse, information hiding, and encapsulation. This is especially helpful in large, real-time systems that are highly parallel and distributed. The paper reviews asemi-preemptionexecution model of object-based real-time systems that simplifies reasoning about the quality of process-to-processor assignment. The model is used to define system properties such as interprocess parallelism, processor utilization, and interprocessor communication. Additionally, an innovative assignment algorithm is presented which incorporates feasibility constraints. The algorithm is guided by an objective that balances minimum communication against maximum parallelism. Experimental results show that the process assignment algorithm performs extremely well with respect to finding process assignments in isolation. The algorithm easily finds process assignments for which a feasible schedule exists as long as the number of items to be scheduled does not exceed approximately 500.