While research demonstrates the importance of numeracy-related activities performed at home for young children's mathematics achievement, few studies involve observational studies of the processes which support children's mathematical learning at home. On this premise, this study reports evidence from numeracy-related interactions between parents and their four-year-old child during cookery sessions at home. Numeracy group parents who received instructions to incorporate additional mathematics into the activity provided significantly more numeracy guidance and also created more opportunities for their children to practice advanced mathematics. Comparison group parents provided enough numeracy guidance to complete the recipe but rarely provided extensive or advanced numeracy guidance. Children in the numeracy group generated significantly more correct math responses during the activity than comparison group children, though there were no significant differences on the post-test. The findings suggest the need to raise parental awareness of opportunities to support and encourage mathematics in activities at home. (Contains 3 tables.)