Many ryegrass cultivars are available on the market, but little research information exists on their comparative drought tolerance or the role of their commercially associated Epichloë endophytes in drought tolerance. Cloned plants of seven perennial ryegrass (Lolium perenne L.) cultivars (Grasslands Commando, Ceres One50, Banquet II, Alto, Bealey, Trojan and Avalon) and an unreleased elite line (URL) and one Mediterranean tall fescue (Festuca arundinacea Schreb.) cultivar (Grasslands Flecha), in all cases both endophyte-free (E–) and -infected (E ) plants, were subjected to a cycle of summer drought and rehydration from December 2012 to May 2013. Other clones of the same plants were irrigated. Insecticide was used to protect plants from insect attack. We report data for shoot dry matter (DM), tiller survival rate (TSR) and reproductive development assessed approximately monthly during the experiment. In the second month of drought, only Banquet II and Grasslands Flecha showed no significant shoot DM reduction under water deficit. After 3 months of drought, shoot DM was reduced by 43% (Flecha) to 85% (URL) compared with irrigated plants. For Banquet II, Avalon and Grasslands Flecha, TSR was not significantly reduced by water deficit. During rehydration, growth of previously non-irrigated plants typically exceeded growth of irrigated clones across all cultivars. Banquet II and Grasslands Flecha were drought-tolerant in the sense that they showed a lower percentage yield reduction under drought than other cultivars tested; this was in part because they were not among the highest yielding under irrigation. Irrespective of irrigation treatment, the shoot DM of E plants of ryegrasses URL (with AR37 endophyte) and One50 (with AR1 endophyte) was reduced by almost 50% relative to their E– counterparts in each harvest from December to May, whereas the other six ryegrass varieties generally showed a small trend towards reduced shoot DM as E plants. This indicates that some novel cultivar–endophyte associations can incur a yield disadvantage compared with E– plants when protected from insect pressure.