In this paper, we examine the grammatical status of el que in Spanish prepositional relative clauses (el lugar en el que vivo) [the place where I live] from a variationist perspective of the theory of grammaticalization. At least from the nineteenth century onwards, several authors have defended the nature of el que as a compound relative pronoun, even if these forms continue alternating today with others without the article [el lugar en que vivo], in contrast to el cual , a fully grammaticalized relative since the late fifteenth century. Based on a 3,200,000 word corpus of immediacy text (mainly private letters), we test the hypothesis of el que being a case of grammaticalization in progress from a variationist point of view, examining in depth what happens inside the grammar and the socio-stylistic matrix in different periods of history, from 1700 to 1960. The idea underlying this approach is that the structure of changes as well as the grammaticalization in progress can be inferred from the comparative analysis between different quantitative magnitudes of functionally similar variants. To do so, we have performed three independent mixed-effects regression analyses ( Rbrul ), one for each century. The results of these comparative analyses confirm the progression of el que in prepositional subordinate clauses between the early eighteenth century and the first half of the twentieth. Yet, this progression has taken place at a slow pace and, objectively, can only be described as moderate. Moreover, a number of elements of continuity in history are revealed, such as several conditioning factors that are systematically selected and with the same explanatory direction in all periods. This casts serious doubt on the existence of a grammaticalization in progress in the case of el que , and sees the evolution as not essentially different from other morphosyntactic changes that have taken place in the history of Spanish.