Context effects are a robust finding in psychology and are manifested in the form of assimilation effects and contrast effects. Assimilation effects occur when judgments of a target stimulus are biased toward the level of non-target, context stimuli. Contrast effects occur when judgments of a target stimulus are biased in the opposite direction of non-target context stimuli and are much more prevalent than assimilation effects. Limited research has been conducted on contrast effects in the area of industrial/organizational psychology and no study has yet examined contrast effects when target and non-target stimuli are observed simultaneously. The purpose of this study was to examine contrast effects in a group interaction setting (a leaderless group discussion (LGD) exercise of an assessment center) where all stimuli were observed simultaneously. Two factors were manipulated: the performance level of non-target stimuli (above standard and/or below standard candidates) and observation condition of the target stimulus (a standard candidate). In addition, the order in which the standard candidate was rated was counterbalanced. It was hypothesized that (1) contrast effects would occur in the LGD. One hundred, eighty-seven undergraduates were trained as raters and then viewed a videotape of a leaderless group discussion exercise in which a standard candidate was interacting either with two above standard candidates, two below standard candidates, or an above standard and a below standard candidate. Each videotape contained the same footage of the standard candidate; consequently, her performance was identical across conditions. Participants were assigned to observe one of the three candidates (the target candidate or one of the non-target candidates). During the rating session when the assessors discussed the performance of the candidates, performance of the standard candidate was discussed in either the first, second or third position. Individual ratings and consensus ratings were collected and analyzed. At the individual rating level, contrast effects were present in leaderless group discussion exercise ratings. Specifically, the standard candidate was rated significantly higher when performing with below standard candidates than with above standard candidates. The observation assignment had no significant influence on the magnitude of contrast effects; however, a leniency effect occurred for those assessors who were assigned to observe the standard candidate. Contrast effects were not present in the raters' consensus ratings. Conclusions, suggestions for future research, and implications for the study are discussed.