Broad-band dielectric spectroscopy in the frequency range from 10(-2) to 10(6) Hz and in a temperature range from 170 to 430 K is employed to study the dependence of the rotation of the mesogenic unit around its long axis (beta-relaxation) on the actual liquid crystalline mesophase in comb-like polymethacrylates. As mesogenic units, derivatives of p-alkoxyphenyl benzoate are used where different mesophases were achieved by small variation of the mesogenic structure and the spacer length. For all samples, the temperature dependence of the relaxation rate of beta-relaxation can be described by an Arrhenius equation whereas both the preexponential factor and the activation energy increase significantly with the order of the mesophase. The width of the dielectric beta-peak decreases with increasing order of the liquid crystalline phase. From these experimental results it is concluded that beta-relaxation in these polymers is a cooperative relaxation process whereas the cooperativity increases with the order of the mesophase.