The present study used a collection of over 400 automated single and multi-word measures to explore their relationship with differences in L2 English writing proficiency based on a graded corpus of 496 writing samples from a widely used language proficiency test. After running correlations between the full range of measures and the score awarded to each essay, we set a conservative minimum correlation cut-off of .30. To account for multicollinearity between significantly correlated predictor variables, in any case where two predictor variables held a minimum correlation of .70 with each other, only one variable was retained. Finally, multiple regression was used to better understand which variables could account for differences in writing proficiency. The most parsimonious regression yielded a model with four predictor variables, total word count, orthographic neighborhood frequency, lexical decision time, and word naming response time accounting for 36% of total variance in writing proficiency scores. These results provide insight into the value of various linguistic features in assessments of L2 English writing proficiency.