The development of patterning strategies during the year prior to formal schooling was studied in 53 children from 2 similar preschools. One preschool implemented a 6-month intervention focusing on repeating and spatial patterns. An interview-based Early Mathematical Patterning Assessment (EMPA) was developed and administered pre- and postintervention, and again following the 1 st year of formal schooling. The intervention group outperformed the comparison group across a wide range of patterning tasks at the post- and follow-up assessments. Children from the intervention group demonstrated greater understanding of unit of repeat and spatial structuring, and most were also able to extend and explain growing patterns 1 year later.contrast, most of the comparison group treated repeating patterns as alternating items and rarely recognized simple geometrical patterns. The findings indicate a fundamental link between patterning and multiplicative reasoning through the development of composite units.