We combine new offshoring and IT workforce micro-data to investigate how an increase in the offshore supply of IT workers has affected the composition of the US IT workforce. We find that at firms with offshore captive IT centers, the relative demand for onshore IT workers in occupations involving tasks that can be traded over computer networks, such as those requiring little personal communication or hands-on interaction with US-based objects, fell by about 8% over the last decade. By comparison, relative demand for workers in those occupations rose by about 3% in firms that were not offshoring. Our second finding is that hourly IT workers are more likely than full-time workers to be employed in occupations requiring tradable tasks, and that the relative demand for hourly IT workers is about 2-3% lower in offshoring firms. We discuss the implications of our findings for IT workers, policy makers, educators, and managers.