Significant incentives remain for decreasing the mean solids and water content and their variability in combined extraction froth from Athabasaca oil sands, both in the hot water processes now commercially implemented, and in projected processes typically operating at lower temperatures. The oil sand can be conditioned in different ways to generate aerated bitumen droplets which can be recovered as a froth by flotation. The froth formation processes determine the quantities of entrained water and solids, and hence froth quality is related to the vertical progression of physical structures in the froth layer. A sampling method was developed to take frozen samples simultaneously from different depths in the froth layer, for the first time, and applied in pilot plant extractions of Athabasca oil sands, operating in either the commercial (Clark) or a development (OSLO) configuration at various temperatures. The patterns of froth structures were rather similar, with minor differences more related to the process temperature than to the oil sand conditioning procedure. The froth structure progressed from loosely packed aerated bitumen droplets at the bottom to bitumen-continuous at the top with an extensive water-continuous middle region containing distorted aerated bitumen droplets and comprising approximately 70% of the total froth depth. An abrupt phase inversion had been expected but was dearly absent. A key factor determining the froth quality appears to be the ability of the bitumen droplets to distort without coalescing, and so to pack more closely allowing continued drainage of the aqueous phase. Implications for froth quality improvement are discussed.