A report is made on the first devices processed using a novel mesa release and deposition (MRD) technique on heteroepitaxial GaAs-on-Si. Mesas are etched, released by under-etching and deposited selfaligned on their original positions. Standard MESFET processing is performed on the MRD structures, demonstrating the suitability of the technique for fabrication of monolithic optoelectronic GaAs devices on Si.