We developed surface-modified silica fillers by coating these with an acrylate monomer, trimethylolpropane triacrylate, or a silane coupling agent, triethoxyvinyl silane, followed by electron-beam irradiation at room temperature. These were incorporated in an ethylene-octene copolymer rubber. Thermorheological studies of the unvulcanized ethylene-octene copolymer and its untreated and modified silica-filled composites were done with a shear dynamic oscillating rheometer. Modification of the silica filler, especially via the silanization process followed by electron beam treatment, significantly reduced filler-filler networking as revealed from the log-log plots of storage modulus and complex shear viscosity, and its real component. The rheological complexity of the compositions was analyzed from a double logarithmic plot of the storage modulus and loss modulus. The results obtained from the master curves constructed on the basis of the time-temperature superposition principle and the activation energy calculated from the Arrhenius equation for the flow of above these compounds further supported these findings. (C) 2003 Wiley Periodicals, Inc.