MicroRNAs (miRNAs) are emerging as cooperating factors that promote the activity of oncogenes in tumor formation and disease progression. This poses the challenge of identifying the miRNA targets responsible for these interactions. In this study, we identify the growth regulatory miRNA bantam and its target, Socs36E, as cooperating factors in EGFR-driven tumorigenesis and metastasis in a Drosophila model of epithelial transformation. bantam promotes growth by limiting expression of Socs36E, which functions as a negative growth regulator. Socs36E has only a modest effect on growth on its own, but behaves as a tumor suppressor in combination with EGFR activation. The human ortholog of SOCS36E, SOCS5, behaves as a candidate tumor suppressor in cellular transformation in cooperation with EGFR/RAS pathway activation.