The world’s longest running field grazing trials were initiated in the Eastern Karoo during 1934 with sheep at Camp-6 by the Grootfontein Agricultural Development Institute (GADI). These sites are situated near the Eastern Cape Town of Middelburg. Other trials were later established at Seligman Old Fields and Bergkamp. As grass began increasing, rotational grazing of cattle and sheet was trialled at Boesmanskop since 1991. The data associated with these trials are of high value due to uniform and uninterrupted management of experimentally well designed grazing trials, as well as accurate and thorough record keeping over the years. GADI maintains the trials, and since 2011 SAEON joined the effort of archiving all existing data and periodic resurveying of the trial paddocks, using the same wheel-point techniques and apparatus as used since the beginning. Data are analysed against the background of 120-year long rainfall records. Rainfall has been increasing in the past four decades, and has shifted from late summer to early summer. Grass abundance and diversity is on the increase, as are the incidents of fire. Continuation of these trials facilitates the detection and interpretation of shifts in vegetation as part of global change.