Summer dormant perennial grasses in the annual rangelands of California's foothills must be managed to maintain productivity. Weed invasion can reduce forage quality and stand persistence and information is lacking on best practices for weed management. Trials were established to assess the effects of indaziflam, rimsulfuron, and aminopyralid herbicides on nine perennial grass species. Herbicide treatments were applied seven years after planting and effects on crop coverage and forage biomass production were evaluated for two growing seasons. Treatment effects on weed populations, perennial grass coverage, and forage biomass varied by planted species. Generally, medusahead invasion was promoted by rimsulfuron treatments, yellow star-thistle was only abundant in the unplanted control, and hare barley was reduced by aminopyralid and indaziflam treatments. The lowest perennial grass coverage was typically observed in the untreated control and the lowest biomass was typically associated with indaziflam treatments. Coverage of wheatgrass and orchard grass varieties was improved by indaziflam treatments. Coverage of Harding grass varieties tended to be greatest in plots treated with rimsulfuron and the highest overall biomass and coverage was achieved in "Perla" koleagrass treated with 70 g ai ha-1 rimsulfuron. Aminopyralid treatments resulted in variable crop coverage effects, but often improved forage biomass through promotion of annual ryegrass. Published by Elsevier Inc. on behalf of The Society for Range Management. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)