The potential supply of water quality mitigation actions from diffuse sources is difficult to assess, although important for designing policies to encourage such actions. In this paper the design and results of a Choice Modelling(CM) valuation to assess the potential supply of rural mitigation actions from altered grazing management are reported. The valuation was focused on the supply of mitigating services (specified riparian management standards), the total cost of provision, and the extent to which these costs varied between landholders. CM has traditionally been applied to environmental valuation issues, but there is increasing use of the method to design agricultural markets. This study extends that application to markets for environmental actions.