A total of forty 24 kg male Dorset weaning lambs were allocated in four dietary treatment groups: ad libitum concentrates (C), restricted concentrates (RC), zero grazing (ZGR), and grazing (GR). Lambs were slaughtered at 47 kg. Meat from grass-fed lambs (ZGR and GR) had a lower ultimate pH (P = 0.04) and L* value (P = 0.03) compared with that from C-fed lambs. However, a*, b*, hue angle, chroma values, shear force, myofibrillar fragmentation index, sarcomere length, as well as fat, protein, and collagen contents were not affected by dietary treatments (P > 0.05). No difference was found in juiciness and tenderness, but typical lamb flavour was more pronounced in C-fed lambs than in GR-fed lambs (P = 0.03). Grazing and ZGR increased the percentage of cis-9, trans-11 C18:2 (P < 0.0001), and total n-3 polyunsaturated fatty acids (PUFA; P < 0.01) and decreased the ratio of n-6/n-3 PUFA (P < 0.0001) in the longissimus dorsi (LD) muscle, whereas C-fed lambs had higher proportion of trans-10 C18:1 (P < 0.0001) and lower proportion of trans-11 C18:1 (P < 0.0001) than the other treatments, which may indicate an altered rumen biohydrogenation. Dietary treatments had minimal effect on meat eating quality but affected meat fatty acid profile.