Jet-cooled fluorescence excitation spectra and selected single vibronic level dispersed fluorescence spectra are presented for p-methoxy-trans-stilbene and p-methoxy-p’-methyl-trans-stilbene. Two stable conformers of the methoxy group are evident in the spectra and are distinguishable on the basis of the difference in their ring torsional frequencies. The lower frequency conformer is the better electron donor. Methoxy substitution lowers the S-1 barrier to internal rotation of the methyl group to similar to 100 cm(-1) compared to 150 cm(-1) for p-methyl-trans-stilbene. The two methoxy conformers have measurably different S-1 barriers. The better donor has the lower barrier, consistent with previous work on p-amino-p’-methyl-trans-stilbene. The spectra also provide evidence of coupling between the ring and methyl torsions and show that methoxy substitution modifies the ring torsional potential energy surface as well.