In this work, a cross-coupled voltage-controlled oscillator (VCO) for the high frequency RFID and citizen bands (CBs) is investigated, and implemented on a flexible Indium gallium zinc oxide thin film transistor (TFT) technology. To circumvent the challenges of integrating passive components in this frequency range and minimize the circuit’s footprint, the resonant tank is designed as a parallel connection of an active inductor with a metal oxide semiconductor capacitor - yielding a total area of 200 µm by 330 µm. The VCO can operate in the CB mode at 10 V power supply, boasting a tuning range from 26.9 MHz to 27.7 MHz and a dc power of 1.93 mW, or in the RFID mode from a 4 V supply, obtaining a 12.9 MHz - 13.6 MHz range at 140 µW dc power. To the best of the authors’ knowledge, this circuit possesses the highest figure-of-merit (frequency/total power), and overall highest oscillation frequency for VCOs reported up to date in comparable technologies.