This chapter has shown that, although no theories of writing is currently available for measuring the writing proficiency of pre-service EFL teachers, a list of nineteen discourse features has been proposed based on the requirements/standards of language teachers regarding writing proficiency, which provides an underlying theoretical foundation for examining the writing proficiency of pre-service EFL teachers. The foregoing review of empirical L2 studies also shows that the attempts have been made to evaluate the essay quality by experimenting with a number of measures. Table 2-5 presents the broad categories underlying the constructs of writing proficiency in the left-hand column. The right hand column presents the relevant measures that have been chosen as operationalization of these constructs, which will be employed in Study One.