The paper proposes a low computational complexity technique based on a polyphase structure for modulation and demodulation of FBMC/OQAM-OTFS signals. This approach effectively reduces the overall computational complexity when compared to the frequency spreading approach (FS-FBMC/OQAM-OTFS), which in turn outperforms the direct modulation and demodulation approach for FBMC/OQAM-OTFS signals (Direct-FBMC/OQAM-OTFS). Simulation results explicitly demonstrate that, for an overlapping factor of K = 4, various PPN-FBMC/OQAM variants can indeed achieve a 2.5–4 times reduction in the computational complexity with an energy loss of no more than 1 dB compared to FS-FBMC/OQAM-OTFS. These obtained results are observed under standard multipath channel profiles such as EPA, EVA, and ETU in both moderately and highly dynamic scenarios. These findings suggest that the PPN-FBMC/OQAM-OTFS technique is a feasible and promising alternative to conventional OFDM in high-mobility wireless scenarios.