We present a full quantum mechanical treatment, using the quantum fluctuation-dissipation theorem, which is useful in describing the absorption line shpae of a system composed of damped vibrational (harmonic) oscillators that are linearly coupled to an electronic excitation. The closed from expressions obtained from the model predict optical line shapes that are identical to standard treatments at high temperature of in the absence of damping. However, at low temperature, quantum corrections become important and the model predicts a skewed optical line shape taht reflects the condition of detailed balance and differs significantly from the "Brownian oscillator" model of Yan and Mukamel [J. Chem. Phys. 89, 5160 (1988)]. We also find that quantum effects become observable in the line shape of the overdamped oscillator only when k(B)T/($) over bar omega(0)omega 0/gamma <1, which effectively depresses the temperature for crossover into the quantum regime. In Appendix D we discuss how the time correlator expressions derived for the line shape analyisis can also be used to describe chemical reactions in the presence of quantum damping. The fact that the transition temperature for quantum bahaviour is dperessed int he presence of strong damping may explain why the "classical" Arrhenius expression is often found to hold, even at temperatures where k(B)T<($) over bar h omega(0). Finally we exploare the consequences of introducing a classical control variable (corresponding to slow conformational motions of a biomolecule), which is coupled to the optically active vibrational mode(s) of the embedded chromophore. This leads to a modulation of the Stokes shift and optical coupling in the system and results in a type of inhomogeneous broadening that has both a Guassian and non-Guassian component. The non-Guassian broadening is found to be consistent with the highly skewed inhomogeneous line shape of deoxymyoglobin.