An earthmoving vehicle powertrain is modeled as a MIMO hydrostatic system. Its control inputs include the engine throttle, an electro-hydraulic pump displacement and flow valve commands. These inputs offer a great control freedom but need to be coordinated. As a starting point for the ultimate MIMO control, a coordinated MISO controller for one of the load nodes is designed by using an LQG technique. Modeling and control design are accomplished and validated by both first principles and experimental data. The experimental data are obtained upon an Earthmoving Vehicle Power-train Simulator (EVPS) at the University of Illinois. The paper details the utilization of this “hardware-in-the-loop” testbed in investigating generic power-optimization problems for hydrostatic transmissions. Simulation results as well as experimental data are presented.