The diet of the powerful owl was studied, by analysis of regurgitated pellets, at Coranderrk Reserve, Victoria; regional variation in the diet was assessed at 4 other sites: Ironbark Basin Reserve, Point Addis: Gormandale; Beaufort; Philip I. The ringtail possum, Pseudocheirus peregrinus, was the most common prey species. Secondary prey species also formed a major part of the diet. The sugar glider, Petaurus breviceps, was important at Coranderrk Reserve and Gormandale, and the Australian magpie, Gymnorhina tibicen, at Ironbark Basin Reserve and Philip I. At Beaufort, G. tibicen and P. peregrinus were equally preyed on. A marked seasonal variation was found in the diet at Coranderrk Reserve: P. breviceps was the major prey item in autumn and P. peregrinus in winter; a number of other prey species were taken when abundant or easy prey. At Coranderrk the powerful owls were estimated to take one major prey item every 1.4 days or about 260 major prey items each year.