In this paper we assess two mechanisms for the production of the thermally transferred optically stimulated luminescence (TT-OSL) signal in quartz when all stimulation is carried out at 125 °C. One mechanism is based on the double transfer process previously put forward for OSL recuperation following storage at room temperature. In this mechanism, electrons from the trap giving rise to the fast OSL component are released by optical stimulation and some are transferred into a refuge trap via the conduction band; these electrons are then released from the refuge trap by a thermal treatment and some are retrapped in the trap responsible for the fast OSL component. The other mechanism is based on a single transfer process in which electrons are transferred by thermal treatment from a light-sensitive trap via the conduction band to the trap that gives rise to the fast component of the OSL signal, this trap having been emptied by the initial optical stimulation. The analysis of the measured OSL and TT-OSL decay curves suggest that the two signals are derived from the same traps and are dominated by the fast OSL component. The experimental data presented support the hypothesis that the original source of the electrons that are thermally transferred is a trap that is less light sensitive than that giving rise to the fast OSL, but one that has similar thermal stability. Thus, a single transfer mechanism explains the production of the TT-OSL signal observed for stimulation above 120 °C when the 110 °C TL trap is kept empty.