This study provides a model for examining the second language (L2) acquisition of structures where the first language (L1) and (L2) are similar, and where native speaker (NS) use varies. Research on the copula contrast in Spanish ("ser" and "estar" mean "to be") has shown that an assessment of learner choice cannot rely on an error analysis (Geeslin, 2001, 2003a; Geeslin & Guijarro-Fuentes, 2004). Obligatory contexts are difficult to identify because norms for copula use with adjectives are changing (Silva-Corvalan, 1994; Guijarro-Fuentes & Geeslin, in press) and NSs vary in their choices for a given context (Geeslin, 2003a). A more effective approach to assessing the acquisition of variable structures incorporates statistical models that identify features of the discourse that best predict copula choice for NSs and nonnative speakers (NNSs). Our research design, which incorporates semantic and discourse-pragmatic constraints, is the first to apply this approach to the acquisition of L2 Spanish by Portuguese-speaking learners. Because Portuguese also possesses copula choice, unlike previously researched L1s, our research also shows that the L2 and the L1 can be compared through analyses based on discourse features and the degree to which each predicts copula choice. Three participant groups were studied: NSs of Spanish ("N"=19), Portuguese-speaking NNSs of Spanish ("N"=11), and NSs of Portuguese ("N"=11). Thus, our definition of NS targets comes from two separate sociolinguistic studies in addition to our study of L2 data. The data elicited using a 28-item contextualized preference task were coded and analyzed according to seven discourse features present in each [copula+adjective] context. Results show that both groups of NSs share the same four predictors, differing only in the level of significance of each. In contrast, the Portuguese NNSs of Spanish are different from each of the other two groups. Our study connects work on the acquisition of Spanish by Portuguese learners to the growing body of research on L2 variation.