Iowa pastures are diverse in the landscapes and soil conditions present within small area units. Introducing legumes into these areas has the potential to improve seasonal distribution and quality of the pasture forage. This study was performed to quantify the spatial and temporal variation in legume contribution to the plant community when seeded into established cool-season grass pastures. Pastures were seeded with a mixture of eleven legumes and then divided into three grazing methods (non-grazed, continuous, and rotational), with each grazing method containing five landscape positions (upland, sideslope, bottomland, opposite sideslope, and opposite upland). Legume dry matter composition, legume species richness, legume diversity, and forage quality was determined during the grazing season and associated with site soil characteristics. Sideslope positions had greater legume dry matter composition (161 g kg-1) than either the upland (62 g kg-1) or bottomland landscape positions (7 g kg -1), and legume concentrations increased as the growing seasons progressed in the grazed treatments. Legume species richness also was greater for sideslope landscape positions. Legume dry matter composition showed a strong, positive linear relationship to species richness in continuous, rotational, and non-grazed treatments (r2 = 0.77, 0.84, and 0.74), and may potentially be utilized as a tool to estimate the need for re establishment in these pastures. Legume dry matter diversity using the Shannon-Wiener index was greatest for grazed pastures, but was positively linearly related to legume dry matter composition in only rotationally grazed paddocks (r2 = 0.88). Upland and bottomland sites with the greatest total available dry matter herbage production potential contained the lowest legume concentrations and legume herbage. Forage NDF was lowest and IVDMD was greatest on sideslopes (527 g kg-1, 630 g kg-1) compared to uplands (552 g kg-1, 608 g kg-1) and bottomlands (568 g kg-1, 560 g kg-1 ). Of all spatial and temporal variables, land slope best explained the variation in legume dry matter composition (r2 = 0.66) and species richness (r2 = 0.75). Competition resulting from the greater grass component at lesser slopes appeared to be a limiting factor for legume establishment. Land slope is easily quantified, and could serve as a basis for pasture division for differential fertilization, seeding, and grazing management.