The prairie area also known as the Grand Prairie, consisting of the Fort Worth Prairie and the Lampasas Cut Plains. There are about seventeen million acres in this region, with one million acres in the Eastern Cross Timbers, about three million in the Western Cross Timbers and about six and one-half million acres in the Grand Prairie. The Eastern Cross Timbers is best described as a mix of the Western Cross Timbers and the Oak Woodlands.

The Oak Woods and Prairies region is gently rolling to hilly with elevation from 300 to 800 feet. Rainfall averages 35 to 45 inches per year with a peak in May or June. Upland soils are light colored, acid sandy loam or sands. Bottomland soils are acid with textures ranging from sandy loams to clays. The Oak Woods and Prairies support large cattle ranches. Oak-hickory forest interdigitates with tall-grass prairies in this region. The Western and Eastern Cross Timbers are major areas of oak-hickory, with open savannah as well as dense brush of post and blackjack oaks. Peat bogs and marshes are distributed along a line corresponding to surface exposures of the Carrizo Sands formations, running roughly southwest from northern Leon County to Palmetto State Park in Gonzales County. River valleys crossing the region support a forest of hackberries and pecans mixed with oaks on the alluvial soils.

The East Cross Timbers is a vaguely defined area along the Red River mainly between Grayson and Clay counties which ends to the south between the Blackland and Grand prairies (Correll and Johnson). The West Cross Timbers lie immediately west of the Grand Prairie.

According to Correll and Johnson, even with the wide variation in soils, the climax understory vegetation is rather uniform with the predominant grasses being little bluestem, big bluestem, Indian grass, switchgrass, Canada wild-rye, side-oats grama, hairy grama, tall dropseed and Texas wintergrass. Brush species also have invaded the prairie, and weedy annual and perennial grasses have increased in number, including hairy tridens (Erioneuron pilosum), Texas grama, red grama (Bouteloua trifida), tumble windmill grass (Chloris verticillata), tumblegrass, red lovegrass and some perennial weeds (Correll and Johnson).