One central task faced by those interested in the corpus analysis of second language writing is how to measure ESL textual sophistication. While many applied linguists have focused on the notion of lexical richness, Robert de Beaugrande has provided the outlines of an approach that highlights the importance of textual efficiency. In his book, Text, Discourse, and Process (1980), Beaugrande defines the wellwritten text as an efficient self-regulating system. If Beaugrande’s definition is accepted, it follows that the majority of ESL texts are inefficient acts of textual communication. In this chapter, the author will explore textual inefficiency by means of the concept of emergent coherence in a corpus of Korean ESL texts. Within the framework of Hallidayean functional linguistics, emergent coherence will be explained in terms of seven principles of textual efficiency: the SPOCA Principle, the Principle of Natural Hierarchy, the Principle of End Weight, the Principle of End Focus, the Principle of Textual Economy, the Principle of Unified Elaborations, and the Principle of Genuine Extensions.