In a 3-year field trial, undersowing of smooth-stalked meadow grass (Pia pratensis L.) and tall fescue (Festuca arundinacea Schreb.) seed crops in cover crops was studied. The selected cover; crops; spring rapeseed (Brassica napus L.), linseed (Linum usitatissimum L.) and field pea (Pisum sativum L.) were assumed to vary in canopy density and canopy closure date. The cover crops were sown in 12- and 24-cm spaced rows. This study shows good establishment and subsequent tiller and fertile tiller production of both grasses, when undersown in all the studied cover crops. Tall fescue undersown in field pea led to a higher seed yield than when undersown in spring rapeseed and linseed. Cover crop row spacing had no observed effect on tall fescue, whereas smooth-stalked meadow grass seed yield was increased when linseed was sown at 24 cm compared to 12 cm rows. When separating autumn tillers of smooth-stalked meadow grass into fractions of <1.5 mm, 1.5–2.0 mm and >2.0 mm stem base diameter all fractions of tillers were positively correlated (r=0.69; r=0.60; r=0.73, respectively) with seed yield.