This study examined the effects of technology-based scaffolds that were composed through the use of the seven-stage, problem-based learning strategy on knowledge construction in a problem-based online asynchronous discussion. In a quasi-experimental setting, 60 students in an undergraduate Instructional Technology and Material Design course were assigned to one of three groups. In one group, students posted messages using a prescribed set of message categories. Using the same message categories, another group completed their messages using suggested sentence openers. A control group received none of the above mentioned scaffolds. Using a multi-method approach (content analysis, measurement of learning performance), the research results showed that technology-based scaffolding in a problem-based online asynchronous discussion improves students' task orientation and leads to more task-related learning activity. Furthermore, using both message labels and sentence openers, which were composed through the use of the seven-stage problem-based learning process theoretical framework, offers an effective strategy for encouraging more elaboration and higher cognitive discourse.