Ignition, quenching, reignition, and consolidation characteristics of high-grade natural Athabasca oil sands when subjected to hot, low-velocity gaseous streams are established. The laboratory tests were conducted using spherical samples of the oil sands in streams of the combustion products of very lean mixtures of hydrogen and air over a temperature range of 630 to 760°C and at atmospheric pressure. Various quenching schemes and rates were employed, the high-temperature spontaneous ignition and/or reignition delay and total burning time, as well as mass losses, were established. Effective activation energies for fresh and prequenched “modified” oil sands samples were then determined. Microstructural changes and sample consolidation behavior were also examined and compared with those observed when the samples were exposed to electrically heated pure air streams under identical conditions.