A new method for measuring magnetic anisotropy in ferrimagnetic powders using applied field Mossbauer spectroscopy has been developed. The method is based on using a uniaxial anisotropy mean-field model to calculate the equilibrium spin orientations as a function of applied field and compute the corresponding Mossbauer spectra. A variety of asymmetric broad line profiles are predicted which are sensitively dependent on the magnetization and the exchange and anisotropy terms. In principle the technique enables the determination of individual sublattice anisotropies, although in the case of pure and Co-Ti substituted barium ferrite the sublattice anisotropies are found to be experimentally indistinguishable. A mean anisotropy is obtained which compares favourably with the results of other measurements on barium ferrite.