In the interior of British Columbia, spring barley (Hordeum vulgare L.) and Italian ryegrass (Lolium multiflorum var. italicum Beck.) are intercropped with fertilizer N as a 1-yr break before reseeding irrigated alfalfa (Medicago sativa L.). Persian clover (Trifolium resupinatum L.) was seeded with barley and ryegrass or only ryegrass to determine its effect on seasonal yield and forage nutritive value. All species mixtures were grown with and without a total of 200 kg ha−1 of N to compare N2 fixation by Persian clover with N fertilizer. Averaged over 2 yr, adding Persian clover to barley-ryegrass provided a total yield that was 96% of that obtained by adding fertilizer N to barley-ryegrass. Second cut yield averaged 58% more with clover than with N. However, the grasses yielded more than the grasses with added clover in the third cut. Adding clover to ryegrass provided 94% of the total yield of adding N fertilizer. Persian clover was higher in crude protein and in vitro digestibility of dry matter than ryegrass, so adding clover tended to improve the nutritive value of mixtures. This was most obvious without N, where Persian clover accounted for more of the total forage produced. The study shows that Persian clover is a valuable addition to barley-ryegrass mixtures; it reduces fertilizer needs, improves mid-season yield and improves forage nutritive value. Key words: Persian clover, barley, Italian ryegrass, forage mixtures