We investigate the origin of stellar halos using a high resolution cosmological SPH + N-Body simulation that includes all the major physical processes involved in galaxy formation self-consistently (Governato et al 2007). This simulation allows us to study the competing importance of dissipative in-situ star formation and accretion off of subhalos in the building of a stellar halo in a $Lambda$CDM universe. We find that the Milky Way-sized galaxy in the simulation is surrounded by a kinematically defined stellar halo with more than one distinct population. We search for tracers of this complex formation history in a sample defined to match a SDSS-like observer. 3-D stellar velocities are analyzed for signatures which might be helpful in understanding the buildup of the Milky Way's stellar halo.