Multiple studies on the relationship between lexical diversity and holistic writing quality in a second language (L2) have consistently shown that a greater number of unique lexical items, compared to the total number of words, is associated with better quality writing. The findings of such studies indicate the importance of vocabulary to L2 writing. However, they provide little information in terms of what vocabulary L2 writers need to learn in order to improve their writing. Despite its limited application in the mid to late 1990s, the use of lexical frequency profiles has not been developed as a method for analyzing the vocabulary of L2 writers’ texts and providing insight as to the vocabulary needed for developing L2 writers. This study constructed two lexical frequency profiles of texts written by a homogeneous group of Spanish-speaking learners of English. Multiple regression analyses were conducted to determine the contribution of more and less frequent lexical items to the participants’ holistic scores. The results indicated that word types which occur less frequently in the English language contributed significantly to the participants’ holistic scores, despite the relatively low frequency with which they were used in the participants’ essays. These results suggest not only the utility of lexical frequency profiles in teaching and researching L2 writing, but also that L2 writers may benefit from instruction using frequency information. Pedagogical implications are discussed in terms of how L2 writing instructors can incorporate lexical frequency information into direct vocabulary instruction.