The spectrum of power radiated by a solid‐state optical maser in steady‐state operation is obtained by considering each atomic system to be a source of randomly fluctuating dipole moment which drives every mode of the cavity. The nonlinear behavior of the collection of atomic systems is treated in such a way that a detailed examination of the distribution of power in the various modes is possible. A number of examples are considered which show how critically dependent on the relative loss rates of the various modes are the characteristics of the output from a multimode oscillator. An interesting result of this calculation is the appearance in some cases of an abrupt transition as the pumping power is increased: above this point a large fraction of energy goes into the mode which is resonant with the atomic transition and which has the lowest loss rate. Another case is studied which does not have this feature, but which could be useful in analyzing the behavior of solid‐state optical masers which have substantial scattering due to crystal imperfections.