In this paper, we address the problem of output feedback tracking control of a class of Euler-Lagrange systems subject to non-linear dissipative loads. By imposing a monotone damping condition on the non-linearities of the unmeasured states, the common restriction that the non-linearities be globally Lipschitz is removed. The proposed observer-controller scheme renders the origin of the error dynamics uniformly globally asymptotically stable, in the general case. Under certain additional assumptions, the result continue to hold for a simplified control law that is less sensitive to noise and unmodelled phenomena.