The effects of diet and levels of dietary vitamin E on lipid oxidation were assessed in lambs in this study. Groups of Suffolk x Lleyn and Scottish Blackface male lambs were fed dietary lipid supplements containing either Megalac (C16:0), or one of two sources of n-3 PUFA: linseed which has a high content of C18:3 n-3, which had been treated with formaldehyde to aid rumen bypass and a mixture of formaldehyde treated linseed plus fish oil to provide EPA and DHA. The diets were based on dried grass had similar levels of fat (60g/kg DM). Vitamin E was included as α- tocopherol acetate at 100 and 500 mg/kg, for the low and high vitamin E diets, respectively. The six dietary treatments were: Megalac with low vitamin E, (ML); Megalac with high vitamin E, (MH); Protected linseed with low vitamin E, (LL); Protected linseed with high vitamin E, (LH); Protected linseed plus fish oil (linfish) with low vitamin E, (LFL); Protected linseed plus fish oil mixture (linfish) with high vitamin E, (LFH). At approximately half of the mature live weight for each breed, animals were slaughtered. This was on average 46 kg for the Suffolk and 36 kg for the Scottish Blackface. The meat from supplemented animals increased susceptibility to lipid oxidation in high PUFA in meat resulted from poor deposition of dietary vitamin E supplements.