The data include biomass, visible leaf injury and senescence, and ACi (net CO2 assimilation rate, A, versus calculated substomatal CO2 concentration, Ci) curves to calculate the photosynthetic parameters Jmax (maximum rate of photosynthetic electron transport) and Vcmax (maximum rate of Rubisco carboxylase activity). Trifolium repens and Lolium perenne were exposed as both monocultures and two-species mixtures to an episodic rural ozone regime in large, well-watered containers within solardomes for 12 weeks. Treatments were elevated ozone (AOT40 (Accumulated Ozone Threshold exposure of 40 parts per billion) of 12.86 ppm h) or control conditions (AOT40 of 0.02 ppm h). The experiments were carried out at the CEH Bangor Air Pollution Facility. The work was funded by the Centre for Ecology & Hydrology Integrating Fund Initiative.