The good optical properties of PQ (phenanthrenequinone)-doped PMMA (poly methylmethacrylate) and the ability to form it in a wide range of substrate configurations makes it attractive as a holographic recording material. Previously Wavelength Division Multiplexing (WDM) and Optical Code Division Multiple Access (OCDMA) filters were demonstrated in this material operating near 1550 nm using edge-illuminated geometry. In this paper we investigate the temperature dependence of edge-illuminated holographic filters formed in PQ/PMMA. It was found that both the volume and refractive index of the material changes as a function of temperature. It was also found that changes to the refractive index dominate the wavelength selectivity of the grating. Experimental measurements and a theoretical model for the grating behavior as a function of temperature are presented.