Detailed calculations of the intermediate scattering function of entangled, binary homopolymer blends are presented. The calculations are based on the reptation model of polymer dynamics and employ the dynamic random-phase approximation for inferring collective blend behavior from single-chain characteristics. The relaxation spectra found here for blends-including the relaxation rates and amplitudes of higher-order modes-a-re contrasted with those for melts and are given for the entire range of length scales from the diffusive to the nondiffusive regime of polymer dynamics. Analytical limits of the intermediate scattering function are successfully compared to numerical results. The dominance of higher-order relaxation modes in specific, experimentally feasible, asymmetric blend systems is indicated, and the possibility of significant deviations of the expected time-correlation functions from a single-exponential decay is noted.