This paper looks into the ability of grid forming inverters to compensate harmonic oscillations of the voltage. The ability to act as a sink for harmonic voltage oscillations is a demanded characteristic for inverter controls to be classified as grid forming. In this paper three methods are used to analyse this ability. At first, an analytical approach is chosen to identify the frequency range in which the grid forming inverter control is damping harmonic voltage oscillations of the external grid. This analytical approach is then verified in simulations, whose scope is then extended to replicate a real voltage grid from a field measurement campaign. To conclude the investigations measurements from a field measurement campaign in an island grid, fed purely by inverters, are analysed. The goal of this paper is to analyse and quantify the ability of grid forming inverters to act a sink for harmonic voltage oscillations, to identify the impact of parameterisation of the inverter control on this ability and lastly to assess the accuracy of analytical and simulation-based approaches to replicate this behaviour.