In many situations of interest turbulent dynamics interacts with mean flows, mean magnetic fields or rotation - this usually makes the dynamics both inhomogeneous and anisotropic. In those circumstances progress can often be made by employing quasilinear approximations and developing equivalent statistical theories. In this talk I will demonstrate the utility of such approaches using models of the joint MHD instability in the solar tachocline and the driving of zonal flows. I will conclude by speculating on how these techniques can be extended to provide self-consistent, efficient sub-grid models of turbulent processes.