We employ fully atomistic molecular modeling to investigate the concentration dependence of the electrooptic coefficient of two guest-host polymer composites. Using classical molecular dynamics, we record the time-evolution of the guest-host system under the application of an external electric field. Through analysis of the orientation of the nonlinear optical chromophores in the guest-host composite with respect to the direction of the external electric field, we calculate the orientational parameter N < cos(3)theta >, with N being the number density of chromophores in the composite. This parameter is directly proportional to the electrooptic coefficient. We find agreement between the concentration dependence of the electro-optic coefficient calculated through our simulation and that from experimental data and also from Monte Carlo models.