Context of learning, such as whether a learner studies a second language (L2) in a formal classroom--"at home" or abroad--may be a key factor in developing grammatical and lexical abilities. Yet, little empirical data is available comparing the effects of study abroad (SA) and formal instruction "at home" (AH) experiences on such development (Freed, 1995). The scant research that exists presents conflicting results (DeKeyser, 1986, 1991; Isabelli, 2002; Lennon, 1990; Regan, 1995; Ryan & Lafford, 1992; Schell, 2001). This paper provides a multivariate analysis (see Biber, 1988) of the effects of learning context on grammatical and lexical abilities in oral conversational discourse. The data compare the abilities of two groups before and after studying Spanish as an L2 for approximately one semester (N = 46): (a) a SA group in Alicante, Spain, and (b) a formal-classroom AH group at an American university. The corpus comprises oral segments produced by the learners in an Oral Proficiency Interview before and after the experimental period. In a corpus-based analysis, each segment was transcribed and tagged for various lexical and grammatical features. In two discriminant analyses, I identified various grammatical and lexical features that differentiated the two groups in terms of program gains. The results indicated that the AH context facilitated more development on discrete grammatical and lexical features. However, quantitative discourse analyses of the corpus revealed that the SA group achieved better narrative abilities and could produce language that was more semantically dense. The data are explained in consideration of the SA group's improved fluency and sociolinguistic pressures that distinguished its learning conditions. (Contains 1 footnote.)