This research suggests utilizing collaborative learning among high school students for better performance on ecology inquiry-based projects. A case study of nine 12th grade students who participated in collaborative learning sessions in the open field and in class is examined. The results show that the students concentrated on discussing the methods of measurement and observation in the open field, rather than the known methods from class or from the laboratory. Another major part of their discussions concentrated on knowledge construction. Knowledge construction occurred between students with same or similar learning abilities. The role of the teacher in these discussions was crucial: she had to deal with and dispel misconceptions; and she had to bridge the gap between low-ability and high-ability students, for enabling meaningful learning to occur. The article ends with a number of recommendations for using collaborative learning as a tool for achieving meaningful learning in high school ecology inquiry-based projects.