Computational techniques are developed for evaluating the Boltzmann orientationally or rotationally averaged single- and multi-photon absorption spectra for molecules interacting with an applied static electric field. The calculations are carried out in the semi-classical dipole approximation, for a plane-polarized sinusoidal time-dependent electric field, through the use of both Riemann product integral and Floquet methods to help solve the time-dependent wave equation. Arbitrary configurations of the applied fields, and of the molecular permanent and transition dipoles, are considered. Applications to three-level models, based on the three lowest electronic states of nitrobenzene, are discussed and used, for example, to illustrate: (1) how the temperature and frequency dependence of the orientationally averaged one- and multi-photon spectra can be sensitive functions of the relative orientations of the relevant permanent and transition dipoles and of the two applied fields, (2) that the temperature and frequency dependence can depend on the photonicity of the transition, (3) neighbouring level effects between two nearly degenerate excited states, and (4) the use of higher photon resonances to resolve strongly overlapping single-photon resonance profiles.