The Osage Plains are a physiographic section of the larger Central Lowland province, which in turn is part of the larger Interior Plains physiographic division. The area is sometimes called the Lower Plains, North Central Plains, and the Rolling Plains. The Osage Plains, covering west-central Missouri, the southeastern third of Kansas, most of central Oklahoma, and extending into north-central Texas, is the southernmost of three tallgrass prairie physiographic areas. It grades into savannah and woodland to the east and south, and into shorter mixed-grass prairie to the west. The Osage Plains consist of three subregions. The Osage Plains proper occupy the northeast segment. Although sharply demarcated from the Ozark uplift, the Plains are nonetheless a transitional area across which the boundary between prairie and woodland has shifted over time. In the central portion of the physiographic area lies the second subregion, the Flint Hills. This large remnant core of native tallgrass prairie is a rocky rolling terrain that run from north to south across Kansas and extends into Oklahoma. To the west and south of these hills are the Blackland Prairies and Crosstimbers. This vegetatively complex region of intermixed prairie and scrubby cedar-mesquite woodland extends into north-central Texas. Bluestem prairies and oak-dominated savannas and woodlands characterize the natural vegetation in the Cross Timbers. Much of the area has been converted to agriculture, although expanses of oak forest and woodland are still scattered throughout the eastern portion of the subregion.

Birds in the Osage Plains include the threatened Greater Prairie-Chicken, Henslow's Sparrow, the Dickcissel, the Loggerhead Shrike, the Field Sparrow, the Scissor-tailed Flycatcher, Bell's Vireo, the Painted Bunting and Harris's Sparrow. Fire suppression, overgrazing and the spread of exotic plants are the factors most negatively affecting priority bird habitat. The area now is managed almost exclusively for beef production with annual burns and intensive grazing practices that provide little of the habitat structure required to support many priority bird species.

Historically, fire, drought, and bison were dominant ecological forces and had great influences on the vegetation from local to landscape scales. The Osage Plains and Flint Hills were dominated historically by tallgrass prairie with scattered groves of oak (Quercus marilandica) in the uplands and along drainages. A variety of wetland types, including wet prairie, marsh and northern floodplain forests occurred along larger rivers. Today, much of the land in the Osage Plains is planted to corn and soybeans, or has been converted to non-native grasses for pasture and hay. Large expanses of tallgrass prairie remain in the Flint Hills where relief is greater than in the Osage Plains subregion and the land less suitable for cropping.