Irrigated tall fescue (Festuca arundinacea: Schreb) was evaluated over four seasons, in the spring and autumn, and was able to maintain a milk production of 15.5 kg FCM/d for medium-sized(550 kg) Friesian cows in mid-lactation, under a lax grazing programme. The response to concentrate feeding was 0.88 kg FCM/kg concentrate fed (as fed basis). The in vivo DOM of the pasture remained relatively high (within the range 61-63) during autumn even as the season progressed, whereas the DOM of the spring fescue declined markedly (from 62 to 57) as the grass set seed. However, this decline in the DOM value was not reflected in the milk production of the cows grazing the pasture, which indicates selective grazing. Keywords:   Milk production, nutritive value, pasture, tall fescue