circuits. An alternative approach using hybrid superconductor-semiconductor JJs can enable a superconducting qubit architecture with full electric field control. Here we present continuous-wave and time-domain characterization of gatemon qubits based on an InAs 2DEG. We show that the qubit undergoes a vacuum Rabi splitting with a readout cavity and we drive coherent Rabi oscillations between the qubit ground and first excited states. We measure qubit coherence times to be T1= 100 ns over a 1.5 GHz tunable band. While various loss mechanisms are present in III-V gatemon circuits we detail future directions in enhancing the coherence times of qubit devices on this platform.