Over the past 45 years, the construct of syntactic sophistication has been assessed in L2 writing using what Bulté and Housen (2012) refer to as absolute complexity (Lu, 2011; Ortega, 2003; Wolfe-Quintero, Inagaki, & Kim, 1998). However, it has been argued that making inferences about learners based on absolute complexity indices (e.g., mean length of t-unit and mean length of clause) may be difficult, both from practical and theoretical perspectives (Norris & Ortega, 2009). Furthermore, indices of absolute complexity may not align with some prominent theories of language learning such as usage-based theories (e.g., Ellis, 2002a,b). This study introduces a corpus-based approach for measuring syntactic sophistication in L2 writing using a usage-based, frequency-driven perspective. Specifically, novel computational indices related to the frequency of verb argument constructions (VACs) and the strength of association between VACs and the verbs that fill them (i.e., verb-VAC combinations) are developed. These indices are then compared against traditional indices of syntactic complexity (e.g., mean length of T-unit and mean length of clause) with regard to their ability to model one aspect of holistic scores of writing quality in Test of English as a Foreign Language (TOEFL) independent essays. Indices related to usage-based theories of syntactic development explained greater variance (R[superscript 2] = 0.142) in holistic scores of writing quality than traditional methods of assessing syntactic complexity (R[superscript 2] = 0.058). The results have important implications for modeling syntactic sophistication, L2 writing assessment, and AES systems.