Orthogonal Frequency Division Multiplexing (OFDM) is combined with Multiple Input Multiple Output (MIMO) systems in recent wireless standards to provide high data rate with reliable communication. Improvement in performance of the system can be achieved when Channel State Information (CSI) is used at the transmitter to perform adaptation. The diversity gains are diminished when the adaptations are done with the delayed outdated CSI. Here we derive the closed-form average Bit Error Rate (BER) expression for Multiple Input Single Output (MISO)-OFDM system, as a function of correlation () between perfect CSI and delayed CSI. Here, we develop an analytical model which explains the effect of feedback delay. The simulation results for analytical model also prove that the diversity gain of considered MISO-OFDM system decreases for .