The effects of grazing experience and presence of adult ewes on the response of lambs to introduction of a novel grass species was examined. Lambs had either been artificially reared indoors or were at pasture with their mothers until they were weaned at 3 months of age, at which time five dry, adult ewes joined them. Grazing occurred in sequence, beginning with one, two, three, and then four grass species in four 1-week periods. Grass species were perennial ryegrass, then timothy, then cocksfoot, and finally red fescue. The total time that lambs spent grazing and ruminating increased by grazing experience and somewhat by the presence of the adult ewes. Grazing experience, and to a lesser extent, the presence of adult ewes, also increased the pasture biting rate (number of bites per minute). There was a compounded effect of grazing experience and presence of adult ewes as well. The most preferred species of grass was timothy, followed by perennial ryegrass. The lambs spent the least amount of time grazing red fescue. The time spent grazing cocksfoot and red fescue was increased by grazing experience, but the presence of adult ewes did not increase the time that the lambs spent grazing novel species. The pasture biting rate was higher for grass species that lambs preferred to graze. Neither experience nor presence of adult ewes increased the biting rate on novel species in the period of their introduction. Although both grazing experience and presence of adult ewes increased the total amount of time spent grazing and the pasture biting rate, only grazing experience increased the acceptability of novel species.