Currently there is a growing interest in the development of optically stimulated luminescence (OSL) dosimeters that may be useful for assessing the neutron flux contribution on the doses in radiotherapy due to neutrons produced in the interaction of megavoltage photon beams. In this work, OSL responses of MgB4O7:Ce,Li with 11B are presented for some photon beams, including 6 MV and 10 MV. For 10 MV, the behavior of the phosphor containing 10B was also evaluated. The material with 10B exhibited an OSL response slightly more intense than that with 11B, indicating a possible application of this new material for dosimetry in photon radiotherapy.