We prove global existence for Einstein's equations with a charged scalar field for initial conditions sufficiently close to the Minkowski spacetime without matter. The proof relies on generalized wave coordinates adapted to the outgoing Schwarzschild light cones and the estimates for the massless Maxwell-Klein-Gordon system, on the background of metrics asymptotically approaching Schwarzschild at null infinity in such coordinates, by Kauffman [23]. The generalized wave coordinates are obtained from a change of variables, introduced in Lindblad [34], to asymptotically Schwarzschild coordinates at null infinity. This in particular gives a simplified proof in the vacuum case with precise asymptotics.