Recent advancements in simulation software and computational hardware make it realizable to simulate a full vehicle system comprised of multiple sub-models developed in different modeling languages. The so-called, co-simulation allows one to develop a control strategy and evaluate various aspects of a vehicle system, such as fuel efficiency and vehicle drivability, in a cost-effective manner. In order to study the feasibility of the synchronized parallel processing in co-simulation this paper presents two co-simulation frameworks for a complete vehicle system with multiple heterogeneous subsystem models. In the first approach, subsystem models are co-simulated in a serial configuration, and the same sub-models are co-simulated in a parallel configuration in the second approach. In order to demonstrate their capability, these two co-simulation methods are applied to a full vehicle system with two sub-models developed in different simulation environments: GT-POWER for the engine and MATLAB/Simulink for the driveline and the vehicle dynamics. The simulation results closely match experimental data, although there exist some discrepancies in their relative magnitudes. However, when compared together, the two co-simulation methods produce nearly the same results, while the parallel simulation could reduce the computation time by 25.7%.