Populations of migratory geese overwintering in Europe have risen rapidly during recent decades, leading to increased pressure on available forage resources and more grazing on agricultural lands. Farmers throughout Europe have complained of yield losses due to goose grazing. In spring, the Svalbard-breeding population of pink-footed goose (Anser brachyrhynchus) migrates through specific staging sites in Norway, where the geese graze on dairy grasslands and other types of agricultural lands in the early growing season. Despite this, little is known of the impacts of goose grazing on hay biomass and quality in Norway. An experiment using exclosures to prevent goose grazing, and plots that were open for grazing, was established in Central Norway to test the effects of variable grazing intensity on dairy grassland yields. A single spring-grazing event had severe negative impact at the site with the highest grazing intensity, leading to a 25% reduction in forage yield (milk feed units per hectare) as compared to ungrazed areas. The impacts on the sites with lower grazing intensity were more subtle. The overall reduction (across all sites) of biomass yield was 26%. Forage quality, in terms of milk feed units per kg, was not much affected. Grazing increased the proportion and diversity of weeds, as evidenced by a 49% increase of the Shannon biodiversity index, and there was a 1·3% decrease in the proportion of herbage biomass of sown species. Hence, we have confirmed farmer reports on yield losses, gaining an increased understanding of the overall farmer costs associated with goose grazing in this northern latitude region.