Background: Collaboration among teachers is now considered a marker of effective schools and key to creating successful professional learning opportunities. However, the nature and efficacy of collaboration vary widely, and research suggests that collaborative efforts often fail to promote teacher development. Purpose: This study draws on goal-setting theory from the organizational and management literatures, as well as prior research on improvement-focused teacher collaboration, to explore specific features of teacher collaborative partnerships developed through the Instructional Partnership Initiative (IPI) in Tennessee. This analysis categorizes the goal specificity and goal commitment of teachers' IPI collaboration and explores individual, relational, and organizational factors associated with high specificity and high commitment. Setting: The IPI is a voluntary statewide teacher development program in Tennessee. Principals pair teachers based on complementary areas of strength and weakness in specific domains of teaching practice based on indicator scores from their teacher observations. Participants/Sample: This study focuses on 48 Tennessee teachers who participated in IPI during the 2016-2017 year and who were interviewed as part of a broader implementation study of IPI. This implementation study purposively sampled schools and teachers who had more robust implementation of IPI. Research Design and Analysis: This qualitative study uses teacher interview data to categorize the goal specificity, goal commitment, and perceived benefits of IPI for 48 participating teachers. After categorizing teacher partnerships using theoretically driven codes, this analysis compared high-specificity/high-commitment and low-specificity/low-commitment partnerships using four illustrative case studies. Findings: Teachers' reported experiences with IPI varied based on the level of goal specificity and goal commitment in their partnership. Teachers in high-specificity/high-commitment partnerships tended to describe more in-depth participation and perceived greater benefits of participation. Teachers' mindsets about improvement, perceptions about teaching expertise, and their principals' approach to implementing IPI all appeared to be associated with the reported level of goal specificity and commitment. Conclusion: As posited by goal-setting theorists, teachers seemed to benefit the most from participating in IPI when they had a specific goal and when they expressed commitment to that goal as a mechanism for their own improvement. The findings reinforce how peer observations can be particularly fruitful sites for collaborative learning among teachers, highlight the challenges of using teacher evaluation data to support collaborative learning, and discuss the important role played by school leaders in implementing teacher collaborative efforts in schools.