Background: Collaborative learning offers benefits, but its potential is often undermined by motivational challenges. This study uses the situated expectancy-value theory to explore how students' expectancies for success relate to group-level regulation of learning during collaborative interactions. The study considers success expectancies both as a motivational condition for and a product of group-level regulation during collaborative learning. Success expectancies are examined both as a condition for and a product of regulated learning, influencing students' engagement in motivation regulation and being shaped by it in turn. Objectives: This study aims to understand the interconnection between group-level regulation and students' success expectancies during collaborative learning and how this sets the stage for learning outcomes. Methods: Forty-eight eighth graders engaged in a four-phase collaborative science task in small groups. Video recordings captured the groups' regulation, and each member completed situational self-reports during different task phases. Stimulated recall interviews conducted after the task explored students' subjective justifications for variations in their situational expectancies for success. Employing multi-channel sequence mining and clustering with mixture hidden Markov models, the study identified two types of group-level regulation sequences: engaged in group-level regulation and occasional cognitive group-level regulation. Results and Conclusions: Findings revealed characteristics of group-level regulation sequences and showed that frequent engagement in cognitive and motivation regulation is associated with more positive success expectancies during and after the task. Success expectancies emerged as both a motivational condition and product of SSRL, correlating with task performance. Qualitative interview findings provided further insights into students' expectancies, shedding light on the motivational dynamics of collaborative learning.