This paper reports an intervention-study where students investigated the role of parameters in quadratic functions through technology-assisted guided discovery. The intervention had three experimental groups of students, each of which used a different type of visualisation – sliders, “drag mode” and a function plotter and one control group. The study provides insight into whether technology-assisted discovery learning supports the conceptualization and understanding of the role of parameters in quadratic functions. Qualitative analysis of students' work investigated the potential and constraints of each of the four different approaches for visualisation. Initial findings showed that technology does support the students in their learning, with the dynamic visualisation groups (drag mode and sliders) showing greater understanding than the function plotter group.