Cool Stars 14 - Submitted Abstract # 39 This version created on 05 October 2006 The YSO Luminosity Function in Serpens as Observed by the Spitzer c2d Legacy Project P. M. Harvey, University of Texas and the c2d Team We describe the process of identifying young stellar objects in the c2d Spitzer Legacy Program studies of star-forming clouds. We discuss in detail the results for the Serpens Cloud where we have IRAC and MIPS observations of a 0.85 square degree area that includes two rich clusters of young stars. The exquisite sensitivity of Spitzer allows us to probe to luminosities appropriate to sub-stellar objects. We describe the YSO luminosity function in Serpens for objects with infrared excesses and compare it briefly to preliminary results for other star-forming clouds in the c2d program. ----------------------------------