This paper proposes an extremum-seeking regulator design based on a Lie bracket averaging technique for nonlinear systems in the presence of unknown disturbance dynamics. The approach adopts a post-processing output regulation method for the regulation of nonlinear systems to the unknown minimum of a measured objective function. The stability analysis demonstrates that one can achieve practical output regulation of the unknown optimum equilibrium. A simulation study demonstrates the ability of the proposed technique to solve general output regulation problems in the absence of exact knowledge of the process dynamics, disturbance dynamics and a corresponding internal model.