Onion is a poor competitor with early-season broadleaf weeds. In addition, there are no current herbicide labels that allow POST application prior to the onion two-leaf stage in ND and PRE herbicide options provide inconsistent results. Bromoxynil and oxyfluorfen at reduced rates plus adjuvants were evaluated in the greenhouse for common lambsquarters and redroot pigweed control and crop safety when applied to onion prior to the two-leaf stage. Bromoxynil and oxyfluorfen plus methylated seed oil (MSO) or petroleum oil concentrate (POC) had the greatest onion safety compared to other tested adjuvants and provided acceptable weed control 12 d after three sequential applications. 14C-oxyfluorfen absorption was evaluated in the laboratory 24 h after treatment and oxyfluorfen absorption was greatest at 35 C compared to 15 and 25 C. Multiple applications of bromoxynil and oxyfluorfen at reduced rates were further evaluated with MSO or POC in field experiments. Bromoxynil provided 12% better common lambsquarters control and 9 t/ha greater large-grade onion yield than oxyfluorfen. Greater reduced rates resulted in greater common lambsquarters control and reduced common lambsquarters stand density. Common lambsquarters control was 24 to 32% greater when POC or MSO were used, respectively, compared to no adjuvant. Bromoxynil did not reduce onion stand/m as rates increased, but oxyfluorfen reduced onion stand as rates increased. Four or five sequential bromoxynil or oxyfluorfen applications every 7 d resulted in 14 to 19% greater weed control than three sequential applications. Onion stand was severely reduced by PRE herbicide and multiple reduced-rate application combinations.