Though discussion of the teacher factor in ICT-enabled science learning abounds in the literature, the investigation of Teacher Enactments (TEs) of ICT-facilitated lessons through exploring teaching practices is still under-explored and under-recognized. Current studies are still lacking in evidence-based findings of TEs based on the investigation of teaching practices. This study explores the TEs of science lessons supported by a web-based learning platform, namely, Collaborative Science Inquiry (CSI), by two experienced teachers in their respective classes. The CSI system is built on a model-based inquiry framework integrated with Computer-Supported Collaborative Learning (CSCL) elements. The CSI lessons selected were on the topic of "Diffusion and Osmosis" in Grade 7. Through examining the ways in which teachers instructed, questioned, and interacted with the students, we identified the commonalities and differences in TEs that subsequently influenced students' conceptual understanding and their involvement in collaborative inquiry. The factors that contributed to these discrepancies were then discussed. Implications were proposed to inform the use of complex ICT tools in the science classroom.