Technical Abstract: Temperate humid grazinglands are an important component of the landscape of the northeastern Unites States. Grass-based agriculture is a major contributor to the economy of this region, but little is known about the basic ecology of these grazinglands. During an eight-year survey of 28 farms across the northeastern United States, we sampled the vegetation on 95 modified Whittaker plots in grazed pastures, and collected data on topography, climate and soils at each site. Surrounding land use and landscape metrics were calculated from the NLCD 2001 within circles of six radii (250 - 2000 m) surrounding each sampling site. Plant species diversity was divided into planned (forage) species and associated (nonforage) species. Composition of forage species was not strongly related to environmental factors or landscape context, while composition of nonforage species was influenced by elements from all classes of explanatory variables, particularly the presence of species in 1000-m2 plots. The lower variability in the forage species pool and the management applied to forage species and only incidentally to nonforage species probably explains the differences in responses of the two groups of species. Seed dispersal pathways may contribute to differences between the two groups. Site management for forage species overwhelms the role of landscape context for this group, but site management alone does not explain all variability in plant species composition. Landscape management, biodiversity management and land use planning must consider pastures as functional plant communities, part of the interconnected regional landscape.