Grandparents are rapidly becoming a key source of childcare for many Australian parents, leading to these secondary caregivers playing an increasingly important role in shaping the nutrition environment and eating behaviours of children. Yet research assessing the quality of the nutritional environmental being provided by grandparents is limited. In addition, research assessing the socio-demographic determinants of grandparents that may influence their food provision practices is lacking. The present study examined the food provision practices of grandparents who provided regular childcare to at least one grandchild aged 3 to 14 years. In total, 1076 grandparents (60% female; average age = 65.07 years) were recruited. Snack provision was reported by a majority of grandparents (82%). Provision of breakfast, lunch, dinner, and snacks was reported by nearly one-fifth (18%) of grandparents. Grandparents most frequently reported providing their grandchild with fresh fruit, followed by milk, cheese or yoghurt. Sugary drinks were least frequently provided. Although these results indicate that grandparents are generally providing a healthy food environment, practices were found to differ by the sociodemographic characteristics of grandparent caregivers and the grandchild in their care. Specifically, males, older grandparents, and those residing in lower socioeconomic suburbs were more likely than females, younger grandparents, and those residing in higher socioeconomic suburbs to provide energy-dense nutrient-poor savoury snacks and less likely to provide fresh fruit, suggesting that these particular segments of the grandparent population may need assistance providing their grandchildren with healthy foods. Overall, the results indicate that grandparents are exerting significant influence on children’s diets and should be considered crucial to efforts to address poor diet quality and childhood obesity.