There are plant-based alternatives to cow's milk that resemble milk in appearance and function, but differ nutritionally. These are associated with lower land use and environmental impact than milk. However, there are places where dairy herds contribute positively to conservation of high nature value pastures through their grazing. The dairy system also produces meat, but it can be questioned how much beef is needed/demanded. This study evaluated the environmental impact of production of oat drink in comparison with production of milk in terms of: i) the necessity for sufficient grazing animals in the landscape for biodiversity conservation; ii) different perspectives on the need for beef and protein; iii) the opportunity cost of land, and iv) the differing protein content of milk and oat drink. The climate impact, eutrophication and acidification potential and ecotoxicity impacts of a typical Swedish dairy farm were calculated and compared with those of the same farm when milk production was replaced by production of oat drink and three different alternatives to dairy beef: 1) beef from suckler herds; 2) chicken; and 3) plant-based protein. In all scenarios, the same area of semi-natural grassland was grazed. The opportunity cost of land use was included by producing bioenergy on spare land. The direct greenhouse gas emissions were considerably lower (16-41%) for all oat drink scenarios than for the milk scenario. When the bioenergy produced on the spare land was assumed to replace diesel, this substitution effect together with the carbon sequestration in soils cancelled out the direct emissions almost entirely when chicken or plant-based protein was produced instead of beef. The eutrophication potential was similar for all scenarios, while the acidification potential was 21-37% higher in the oat drink scenarios due to the need for handling increased amounts of digestate from bioenergy (biogas) production. This explorative study demonstrated great potential for reduced climate impact through production of oat drink instead of cow's milk, while still preserving grazing services for biodiversity conservation. However, for this to happen, incentives to manage semi-natural grassland need to be introduced, as such management is not an inherent effect of oat drink production. In addition, for the environmental benefits demonstrated in this study to come about, consumers must be incentivised to consume oat drink instead of milk and, to achieve the largest climate impact reductions, to replace some beef with chicken or cereals and legumes.