Integrating science, technology, engineering, and mathematics (STEM) subjects in pre-college settings is seen as critical in providing opportunities for children to develop knowledge, skills, and interests in these subjects and the associated critical thinking skills. More recently computational thinking (CT) has been called out as an equally important topic to emphasize among pre-college students. The authors of this paper began an integrated STEM+CT project three years ago to explore integrating these subjects and literacy in a curriculum for 5-8-year-old students. We reported on the development of this project and an analysis of how the existing curriculum highlighted CT knowledge and skills, and how we expected the curriculum to engage students in CT in an ASEE conference paper in 2016. This paper reports on the evolution of the project and curriculum. Part of this evolution included the defining of CT and its associated competencies and what it would look like for this young age group. In this paper, we discuss this evolution as well as how we have operationalized the competencies with data from classroom testing. At the outset of this project, there were few resources that specifically considered teaching CT with 5-8-year-old children and fewer clear examples of what it looked like for children to engage in CT. However, there were many, sometimes competing, definitions and approaches to CT more generally. After further review of the literature and classroom testing of our revised curriculum, the team developed definitions for the following CT competencies: abstraction; algorithms and procedures; automation; data collection; data analysis; data representation; debugging/troubleshooting; problem decomposition; parallelization; simulation; and pattern recognition. Analysis of hundreds of students and tens of teachers implementing the curriculum allowed us to develop concrete examples of how students engage in CT competencies as well as how kindergarten through second grade teachers foster CT competency development. We report on these examples and how they informed the development of the integrated STEM+CT curriculum.