Mislevy’s sociocognitive perspective on assessment argues that examinees’ linguistic, cultural, and substantive (LCS) patterns serve to organize their ways of knowing and their knowledge construction. In this study, we used a purposefully designed prompt to obtain essays from 70 Chinese undergraduate English majors and 66 American undergraduate students to illustrate LCS patterns conveyed in texts produced by students in collectivistic and individualistic cultures (i.e., China and United States). We found that linguistically, compared to American students, Chinese students used more adjectives, adverbs, modal verbs of obligation, and were more direct in offering value judgements; culturally, while the texts from the two groups yielded overlapping themes, there were clear group difference in the rank order of number of codes for the themes and in the supporting text for each theme; substantively, there were noticeable group difference in the conceptualizations of how the themes were related to each other. Because it remains unknown how cultural and substantive features expressed in L2 essays may affect writing assessment, these differences presented both challenges and opportunities for the field of writing assessment. Implications for the equity and validity of L2 writing assessment were discussed.