Tall fescue (Festuca arundinacea Schreb.) infected with an endophyte that does not produce ergot-like alkaloids (nontoxic endophyte) has not been evaluated for herbage mass, nutritive value, and ergovaline concentration when stockpiled during winter. Our objective was to quantify these responses for tall fescue infected with a native endophyte (K31 E+), a nontoxic endophyte (HiMag NTE), and with no endophyte (HiMag E-). Responses were measured on a fine, mixed, active, mesic Oxyaquic Fragiudalfs soil monthly from mid-December through mid-March in 1999-2000 (Year 1) and 2000-2001 (Year 2) in southern Missouri. Herbage mass for K31 E+ averaged 2370 kg ha-1, which was ≈20% greater than HiMag E- or HiMag NTE. Herbage mass did not change from mid-December through mid-March for any entry. The nutritive value of all entries was equal on comparable dates with acid detergent fiber (ADF) ranging from 285 to 338 g kg-1 during the winter. Nutritive value was highest in mid-December of each year and then declined slowly after that. Neither HiMag E-nor HiMag NTE contained ergovaline, but K31 E+ had substantial concentrations of ergovaline in both years. The ergovaline concentration of K31 E+ was 454 μg kg-1 in December of Year 1 and 175 μg kg-1 in December of Year 2, but declined by ≈85% by March each year. The stable herbage mass, slowly declining nutritive value, and absence of ergovaline in HiMag E- and HiMag NTE suggest that livestock producers could eliminate toxicosis problems by stockpiling these forages for winter grazing.