This study examined the impact of structuredness of asynchronous online discussion protocols and evaluation rubrics on meaningful discourse. Transcripts of twelve online discussions involving 87 participants from four sections of a graduate course entitled Instructional Technology Foundations and Learning Theory were analysed across four semesters. Protocols and evaluation rubrics guiding online discussions in this course ranged from minimal structure or loosely defined protocols in the first section, to high structure or well defined and comprehensive protocols and evaluation criteria in the fourth section. The analyses revealed that some elements of structure had a significant impact on meaningful discourse. Particularly, guidelines that assisted the facilitation and evaluation of online discussions increased the cognitive quality of student postings promoting a deeper and more meaningful understanding of course content.