Transmission voltage-level photovoltaic (PV) plants are becoming reality in many developed and developing countries around the world. Studies suggest that large-scale PV plants could have either positive or negative influence on low-frequency oscillation (LFO) depending on their locations and sizes. Given the fact that these plants cannot be placed in ideal locations to minimize their impact on LFO, it is important to consider designing a damping controller for flawless integration. In this paper, a minimax linear quadratic Gaussian-based power oscillation damper (POD) for a large-scale PV plant is proposed for interarea oscillation damping. A benchmark power system prone to power system oscillations is used to demonstrate the damping performance of the designed controller considering feedback signal transmission delay. The performance of the designed controller is evaluated under different operating conditions as compared to the classical POD at PV plant. Simulation results demonstrate that the proposed controller for a PV plant provides sufficient damping to the interarea mode for a wide range of operating conditions.