Group-oriented contingencies are arranged to target the behavior of a group of people simultaneously. Overall, group-oriented contingencies have been shown to be effective in both decreasing problem behavior and increasing appropriate behavior. However, results are mixed regarding which type(s) of group-oriented contingency is most effective for changing behavior. In addition, although there are anecdotal reports of positive and negative side effects when using group-oriented contingencies, little research has involved direct measurement of these potential side effects. The purposes of the current study were to (a) compare the effects of three types of group-oriented contingencies for increasing on-task behavior and decreasing problem behavior, (b) determine whether implementing a group-oriented contingency for one behavior resulted in changes in a non-targeted behavior, and (c) determine how often and under what conditions side effects occurred within group-oriented contingencies conditions for two groups of preschool children. The results of the study were mixed. The results suggested that group-oriented contingencies were effective in decreasing problem behavior and increasing on-task behavior, but varied across groups as to which contingencies were the most effective at changing both behaviors. Secondary data suggested that side effects were associated with group-oriented contingencies, as well as the occurrence of problem behavior and reinforcer delivery.