We report multifrequency radio observations of GRO J1655-40 obtained with t
he Australia Telescope Compact Array, the Molonglo Observatory Synthesis Te
lescope and the Hartebeesthoek Radio Astronomy Observatory at the time of t
he major hard X-ray and radio outbursts in 1994 August-September. The radio
emission reached levels of the order of a few Jy and was found to be linea
rly polarized by up to 10%, indicating a synchrotron origin. The light curv
es are in good agreement with those measured with the VLA, but our closer t
ime sampling has revealed two new short-lived events and significant deviat
ions from a simple exponential decay. The polarization data show that the m
agnetic held is well ordered and aligned at right angles to the radio jets
for most of the monitoring period. The time evolution of the polarization c
annot be explained solely in terms of a simple synchrotron bubble model, an
d we invoke a hybrid "core-lobe" model with a core which contributes both s
ynchrotron and free-free emission and "lobes," which are classical synchrot
ron emitters.