A study is presented of the skills that primary pre-service teachers (PPTs) have in completing the planning of a scientific inquiry on the basis of a guiding script. The sample comprised 66 PPTs who constituted a group-class of the subject "Science Teaching," taught in the second year of an undergraduate degree in primary education at a Spanish university. The data was acquired from the responses of the PPTs (working in teams) to open-ended questions posed to them in the script concerning the various tasks involved in a scientific inquiry (formulation of hypotheses, design of the experiment, data collection, interpretation of results, drawing conclusions). Data were analyzed within the framework of a descriptive-interpretive qualitative research study with a combination of inter- and intra-rater methods, and the use of low-inference descriptors. The results showed that the PPTs have major shortcomings in planning the complete development of a guided scientific inquiry. The discussion of the results includes a number of implications for rethinking the "Science Teaching" course so that PPTs can attain a basic level of training in inquiry-based science education.