Supplemental Instruction (SI) is a peer tutoring system shown to increase course grades and reduce dropout, particularly for courses with significant failure/dropout rates. Unfortunately, such systems can place significant time and resource demands on faculty, SI personnel, and higher education institutions, all of which pose impediments to their adoption. Given this concern, an assessment of a less resource-taxing version of SI is presented. Across three sections of Introductory Psychology, 30%-42% of enrolled students attended at least one lower-resource group tutorial session. These students performed significantly better on course exams than did non-attendees, by as much as a letter grade. Further, those who attended more sessions earned higher final course grades. These performance differences do not appear to be due to selection bias; session attendance predicted grades on four of the five course exams, even after controlling for students' academic ability and motivation. Students who did not participate cited time constraints as the primary reason. Those who did participate perceived most session activities as highly beneficial, especially completing a pre-session study guide and reviewing the answers in-session. Thus, the present tutoring program appears to represent an effective, efficient method of achieving desirable academic outcomes that students regard as worthwhile.