In this work we investigate the effect of visible light radiation on compact 1T-1R relaxation spiking oscillator cells based on 2-terminal Vanadium dioxide (VO2) structures. We illuminate the devices using a tunable wavelength laser between 400 and 850 nm at power levels ranging from 1 to 70 mW. We observe a strong dependence between the insulator-to-metal switching thresholds of VO2 and the power and wavelength of incident radiation. In addition, we find that the dependence of DC switching characteristics (switching thresholds, R-OFF and R-ON) on light intensity clearly affects the free running frequency of the 1T-1R oscillator, which enables the circuit to function as a power-to-frequency transducer across a wide of wavelengths in the visible spectrum. Excellent transducing linearity of the proposed light-to-frequency conversion is reported in all investigated visible light spectrum. This work is a significant step forward in the field of spiking VO2 oscillators as light transducers for future IoT and neuromorphic applications.