This paper explores the ways in which 'good teaching' is constructed through mentors' written lesson observation feedback during Initial Teacher Education (ITE). Written lesson observation feedback has received little research attention, yet represents a potentially powerful activity for teachers' development. It is also an important aspect of direct university-school-beginning teacher collaboration which is common across diverse programmes and ITE partnerships internationally. Data were collected from written lesson observation feedback given to beginning teachers (n=127) on one ITE programme in England across oneyear to a total of 508 lessons, and analysed through a typology of competing conceptions of teaching defined by Winch et al.: craft, executive technician, and extended professional. These data suggest that teaching is predominantly constructed through mentors' written feedback as a craft or technical activity. In response, we argue that there is scope to broaden the evidence considered, in particular by bringing observed insights about beginning teachers' practice into dialogue with research evidence to construct a more expansive vision of teaching as a professional endeavour. This paper extends previous work on written lesson observation feedback through a larger scale empirical study, and by connecting the practice with broader attempts seeking to improve teachers' engagement with research evidence.