We present deep spectroscopic and imaging data of the host galaxies of Mrk 1014, IRAS 07598+6508, and Mrk 231. These objects form part of both the QSO and the ultraluminous infrared galaxy (ULIG) families, and may represent a transition stage in an evolutionary scenario. Our imaging shows that all three objects have highly perturbed hosts with tidal tails and destroyed disks, and appear to be in the final stages of major mergers. The host galaxies of the three objects have spectra typical of E+A galaxies, showing simultaneously features from an old and a young stellar component. We model spectra from different regions of the host galaxies using Bruzual & Charlot spectral synthesis models using two component models including an old underlying population and recent superposed starbursts. Our results indicate a strong connection between interactions and vigorous bursts of star formation in these objects. We propose that the starburst ages found are indicative of young ages for the QSO activity. The young starburst ages found are also consistent with the intermediate position of these objects in the far infrared color-color diagram. (abridged)
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