In a long term study, yield of wheat or canola on summerfallow was influenced very little by rotation. On the other hand, yield of wheat or barley grown on stubble was affected by rotation. Yield of wheat on canola stubble was generally higher than on wheat stubble. Yield of hay was highly variable from year to year. Yield of canola relative to wheat was much higher during 1980 to 1991 than reported for 1972 to 1979. Further, yield variability of canola between years was much lower during 1980-91 than 1972-79. In wheat monoculture rotations, yield variability increased as summerfallow frequency decreased. In rotations of canola with cereals and/ or a forage the same trend did not occur. The influence of these results on economic viability of rotations where summerfallow is practiced less frequently is discussed.