This paper presents a low-cost approach for testing RF ZigBee transmitters using only a standard digital ATE. The proposed solution permits to implement symbol error detection. The approach is based on 1-bit under-sampled acquisition of the RF signal (2.4GHz OQPSK-modulated signal with half sine pulse shaping). A dedicated post-processing algorithm is then applied, which (i) extracts the phase information from the captured binary sequence, (ii) reconstructs the RF modulated signal and (iii) performs the demodulation. The different steps of the post-processing algorithm are detailed in this paper. The robustness of the post-processing algorithm to various imperfections, both in the signal under test and in the acquisition equipment, are investigated with numerical simulations. Finally, experimental results obtained with NXP ZigBee transceiver fully validate the ability of the proposed method to retrieve the symbol sequence present in the RF modulated signal using the simple binary capture.