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Usable space has been reduced by the increase of non-native, invasive grasses over a considerable portion of South Texas. These grasses generally form high density monocultures and often are associated with increased herbaceous vegetation height, losses of forb and native grass diversity, and reduction of bare ground cover. Tanglehead (Heteropogon contortus), a native grass, recently has acted as a non-native, invasive, increasing rapidly and forming high-density monocultures in the western Sand Sheet area of South Texas. Consequently, tanglehead may be negatively influencing the structure and floristics of northern bobwhite (Colinus virginianus) habitat on native rangelands in South Texas. The objective of our research was to determine the relationships between tanglehead and habitat characteristics considered important for bobwhite habitat. We surveyed 20,103 hectares on 4 ranches during spring 2015, measuring vegetation on 488 transects. We measured tanglehead canopy cover, forb and grass species richness, bare ground, herbaceous vegetation height, and shrub cover at each transect. We also determined the soil series at each transect. We modeled the relationships between tanglehead and vegetation factors using quantile regression, at the 10th, 50th, and 90th quantiles, while soil relationships were determined graphically. We found significant negative relationships between tanglehead cover and forb and grass species richness, bare ground, and shrub cover at all quantiles. Tanglehead cover showed a significant positive relationship with vegetation height for all quantiles. Tanglehead cover was highest on reddish-brown, loamy fine sandy soils of the Comitas and Delmita series. Our results demonstrate the negative effects of increased tanglehead cover on native rangeland habitats. Increases in vegetation height as well as reductions in vegetative diversity and bare ground can have negative impacts on the wildlife community, notably grassland birds such as bobwhites. Further expansion by tanglehead has the potential to significantly reduce both range and wildlife habitat quality in South Texas.