An endogenous oil extracted from Brassica seeds is disclosed that contains, after crushing and extraction, greater than 86% oleic acid and less than 2.5% .alpha.-linolenic acid. The oil also contains less than 7% linoleic acid. The Brassica seeds are produced by plants that contain seed-specific inhibition of microsomal oleate desaturase and microsomal linoleate desaturase gene expression. Such inhibition can be created by cosuppression or antisense technology. Such an oil has a very high oxidative stability in the absence of added antioxidants.