This dataset consists of experiment data that was used to design a framework for constructing cover crop mixtures and validation data that was used to test the effectiveness of the models within the framework. The framework was developed using data from a field experiment, which included six response surface designs of two-species mixtures, as well as a factorial replacement design of three- and four-species mixtures. We quantified intra- and interspecific competition among two grasses and two legume cover crop species with grass and legume representing two functional groups: pearl millet [Pennisetum glaucum (L.) R. Br.], sorghum sudangrass [Sorghum bicolor (L.) Moench × S. sudanense (Piper) Stapf], sunn hemp (Crotalaria juncea L.), and cowpea [Vigna unguiculata (L.) Walp]. Yield-density models were fit to estimate intra- and interspecific competition coefficients for each species in biculture. Competition coefficients were used to build models that estimated the biomass of each cover crop species in three- and four-species mixtures. The competition coefficients and models were validated with an additional nine site-years testing the same cover crop mixtures. Accounting for competition when constructing cover crop mixtures can improve the ecosystem services provided, and such an advancement would likely lead to greater farmer adoption.