Blogging has become very popular in different educational fields, including second language teaching. This article arises from the need to research the impact that the implementation of blogging has on the acquisition of certain language competences. The main objective of the study was to research the impact of the use of blogging on the development of writing skills in the foreign language (L2). Students, divided into four groups, were asked to write a number of descriptive essays in which they could reflect both on the theoretical and practical contents seen in class. Using statistical tools such as Coh-Metrix to establish the errors that Spanish engineering undergraduates make when writing in English, the metrics of their texts were compared to the metrics resulting from a set of reference texts. Findings revealed that the use of blogging was positive in the four different groups. The high correlation between the grades awarded to students' essays by the teachers and those given by the Coh-Metrix tool showed its effectiveness in the study of the linguistic and discursive indices of the English texts produced by students.