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Monocultures of the perennial prairie grass, switchgrass (Panicum virgatum), are expected to supply feedstock for advanced biofuels. Although switchgrass is able to produce high biomass yields across a wide range of topographic sites, other native species might outyield switchgrass within their zones of adaptation. Such species could enhance diversity and ecosystem services provided by biofuel fields. In a small-plot, replicated experiment, switchgrass and members of three functional groups (warm-season grass, cool-season grass, and forb) were planted in monocultures at three slope positions (shoulder, mid, and foot) of a working farm in eastern South Dakota. The field had previously been in a corn (Zea mays)-soybean (Glycine max) rotation. Species used for each functional group varied with slope position. Species were matched with slope positions where they were best adapted. At each position, switchgrass was also combined with each functional group in binary mixtures such that switchgrass consisted of 33 or 67% of each mixture. All plants were transplanted into the field in mid-June 2012 and harvested in autumn of 2012-2014 (anticipated). Through 2013, results indicated potential for several species, especially warm-season grasses and cup plant (Silphium perfoliatum), to mix favorably with switchgrass while equaling or exceeding switchgrass monoculture biomass production (p < 0.05). As a group, cool season grasses performed poorly relative to switchgrass. Across the landscape in 2013, biomass could have been maximized by planting a little bluestem (Schizachyrium scoparium; 67%)-switchgrass (33%) mixture at the shoulderslope, a big bluestem (Andropogon gerardii) monoculture at the midslope, and a cup plant monoculture at the footslope. Alternative high-yielding combinations of species could be selected to meet other objectives, such as maximum species richness, functional groups, or economic returns. Future research should apply the concepts developed in this experiment to additional species and field-scale plots.