Early symptoms of ASD develop through the second year of life, making a stable ASD diagnosis possible at 24 months of age. However, in general, children with ASD have their diagnosis at an older age. This retrospective study, including 30 children with ASD and 30 control children aged 3–6 years, explored the possibility of developing a short observation list to be used in day care settings for children 12–24 months of age. From 73 symptoms selected from published screeners and observation tools, we were able to construct a list of six symptoms that retrospectively differentiated children with ASD from typically developing children at 12–24 months of age when recalled by day-care personnel.