This paper evaluates the validity of teaching English grammar to preservice teachers in a teacher education course at a regional university. The course was delivered in blended mode using the grammar component of My Writing Lab Global (MWLG) and face-to-face instruction. The aim of this study was to establish if there are benefits to derive from teaching knowledge about language (KAL) to preservice teachers. Our quasi-experimental study found MWLG was well-received by participants who believed it had improved their KAL; this improvement was confirmed by 10% improvement on a pre and post KAL test (p < 0.001). MWLG scores and the KAL test also reliably predicted other academic competencies: the students' accumulated GPA and their final written assessment scores for the course (r= 0.4 to 0.54; p < 0.01). Collectively, these findings suggest that explicit KAL is valued and valid knowledge and should be included in teacher education programs.