||Old World bluestems (Bothriochloa spp.) have been seeded on over a million hectares of marginal farmland in Oklahoma and Texas, yet we know little about their regrowth yield and quality, The objective was to determine seasonal pattern of forage regrowth yield and quality of leaves and stems of WW-Iron Master (B. ischaemum [L.] Keng) and Caucasian (B. caucasica [Trin.] C.E. Hubb,) bluestem when 4-week regrowth was harvested at weekly intervals from early May through mid-September, Four plots of each bluestem were established in each of the 4 blocks (32 plots total). Harvesting was rotated so that 4-week regrowth of each bluestem was harvested weekly from 1 of the 4 plots in each block during 1988 and 1989 to determine regrowth yield, in vitro dry matter digestibility (IVDMD), and crude protein (CP) of leaves and stems, Forage regrowth of both species peaked in June both years, Regrowth during August averaged 10 and 35% of June regrowth in 1988 and 1989, WW-Iron Master produced 80 and 45% greater 4-week regrowth than Caucasian in 1988 and 1989. WW-Iron Master produced 75 and 28% greater leaf regrowth than Caucasian in 1988 and 1989 and twice as many stems both years, Leaf and stem IVDMD of WW-Iron Master averaged 2 to 6 percentage units higher than Caucasian, Leaf CP of WW-Iron Master averaged 2 percentage units higher than Caucasian during May and June, However, stem CP of WW-Iron Master averaged 1 percentage unit lower than Caucasian. Grazing management plans need to consider that the majority of bluestem forage production was restricted to a 1 month period in June. This technique of sampling 4-week regrowth every week during the growing season was an effective method for determining the seasonal regrowth pattern.