This paper studied the steady state response of infinite beams supported by nonlinear viscoelastic foundations with 4-parameters. A moving harmonic concentrated load was considered, and the nonlinear foundation was assumed to be cubic. The domain decomposition method was used to deal with the nonlinear term of the foundation reaction, and the complex Fourier transformations, Green′s function, and the theorem of residues were employed to determine the steady state response of the infinite beam on a nonlinear foundation. The numerical examples were used to investigate the effects of the frequency and the speed of moving harmonic load on the steady state responses of infinite beams supported by nonlinear foundations. Moreover, the influences of the nonlinear elastic parameter and the shear modulus of foundations on the steady state responses were also studied.