The interlayer exchange coupling has been investigated in epitaxial Fe(20 Angstrom)/Cr/Fe(20 Angstrom)/Ag/GaAs(100) structures that contain a wedge-shaped (0-40 Angstrom) Cr layer. Longitudinal and polar magneto optical Kerr effect (MOKE) and Brillouin light scattering (BLS) measurements have been combined to determine values for the bilinear and biquadratic coupling strengths. While the phase and period of the oscillations in the interlayer coupling agree well with those reported by other researchers, the magnitude of the coupling strength is found to be reduced. The dependence of the biquadratic coupling strength upon the Cr thickness is well described by a simple power law and may provide a useful test of extrinsic biquadratic coupling models. We show that the combination of MOKE and BLS measurements are very effective in investigating the ultrathin Cr region and that ferromagnetic (FM) coupling produces large changes in the polar MOKE saturation field.