These hills are those around the Lake of the Ozarks along the Osage river and the Gasconade river which are both tributaries of the Missouri river, located in the state of Missouri, to the northwest of Saint Francois Mountains. The region covers 5,040 square miles (13,100 km2) within Missouri.

The Osage-Gasconade Hills ecoregion is more densely forested and dissected than the lower relief Springfield and Salem Plateaus to the south. Steep slopes and narrow ridges of carbonate and sandstone underlie the rocky and thin soils throughout the ecoregion.

River and streams flow generally northward and all drain into the Missouri River. In the area are numerous caves, springs, calcareous wet meadows, and streams with entrenched valley meanders are common. Losing streams are also found in this ecoregion, which streams include disappearing stream, influent streams or sinking rivers are a type of waterway that loses water as it flows downstream

The natural vegetation is predominantly mixed oak forest, with oak-pine forest and some pine forests in the southeast areas of the region. There are also some small limestone and sandstone glades. The northeastern edges of this region are transitional and blend into the Interior River Valleys and Hills ecoregion.