We have defined a new, complete, low-frequency selected sample of southern radio quasars, the Molonglo Quasar Sample, with the aim of studying the aspect dependence of the radio and optical emission. As a test for enhancement of the optical continuum, we find that the narrow [O II] and [O III] emission line equivalent widths decrease systematically with radio core dominance. This effect is consistent with the optical continnum being relativistically boosted at angles close to the line of sight. However, such an interpretation seems to be in conflicts aith the aspect independent behaviour of the broad lines, most notably Kβ
