A principle attribute of perennial grasses for biomass is the potential for high yields on marginal land. The objectives of this study were to evaluate perennial native warm-season grasses [i.e., switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerardii) (BB)], intermediate wheatgrass (Thinopyrum intermedium) (IW), and corn (Zea mays) for their potential to produce biomass as affected by harvest timing and manure application on backslope (not suitable for corn production) and footslope (suitable for corn production) positions. Grasses were harvested at anthesis (summer), after a killing frost (fall), or allowed to over-winter in the field and harvested the following spring (spring) from 2003 to 2006. Two rates of beef cattle (Bos taurus) manure (target rates of 0 and 145 kg total-N/ha) were surface applied during spring. Maximum annual biomass yield on backslopes was 5.4, 4.6, 4.5 and 5.1 Mg/ha for switchgrass, big bluestem, intermediate wheatgrass, and corn, respectively. Biomass yields were not different between fall and over-wintered, spring harvest treatments. With normal precipitation, biomass of switchgrass, big bluestem, intermediate wheatgrass, and corn on backslopes was 96%, 86%, 86%, 85% of biomass on footslopes, respectively. Manure application increased production approximately 30% from the second year (2004-2006) on both landscape positions but had no effect the first year (2003). These results demonstrate the potential to utilize switchgrass and big bluestem as dedicated bioenergy crops on marginal land. Furthermore, it may be possible to allow the crop to over-winter in the field without losing significant biomass.