Native perennial grass competition can substantially reduce the invasion of Nassella trichotoma (serrated tussock), a major perennial grass weed problem in south-eastern Australia. This paper reports on a field experiment that investigated the recruitment of N. trichotoma seedlings, and determined what level of native grass competition was needed to prevent establishment in the central-west of NSW. Grasslands that maintained >2 t dry matter (DM)/ha and 100% ground cover (measured in spring) prevented N. trichotoma seedling recruitment. Relatively small amounts of perennial grass (>0.5 t DM/ha measured in spring) resulted in mortality of N. trichotoma seedlings that had recruited earlier in the year, through the next summer. Flupropanate also markedly reduced native perennial grasses and substantially increased N. trichotoma seedling establishment 12 months after application. Rotational grazing to maintain adequate levels of DM was an important management tactic that prevented N. trichotoma establishment and survival.