Purpose: This study adds to the Lidcombe Program evidence base by comparing individual and group treatment of preschoolers who stutter. Method: A randomized controlled trial of 54 preschoolers was designed to establish whether group delivery outcomes were not inferior to the individual model. The group arm used a rolling group model, in which a new member entered an existing group each time a vacancy became available. Assessments were conducted prerandomization and 9 months and 18 months postrandomization. Results: There was no evidence of a difference between treatment arms for measures of weeks or clinic visits required, percent syllables stuttered, or parent severity ratings. However, children in the group arm consumed around half the number of speech-language pathologist hours compared with children treated individually. In addition, children in the group progressed more quickly after the treating speech-language pathologist became more practiced with the group model, suggesting the group results are conservative estimates. Conclusions: Group delivery of the Lidcombe Program is an efficacious alternative to the individual model. Parents responded favorably to the group model, and the treating speech-language pathologists found group treatment to be more taxing but clinically gratifying.