The objectives of this study were to determine if the level and consistency of glyphosate-resistant (GR) horseweed control prior to soybean planting may be improved with a) the addition of halauxifen-methyl, 2,4-D ester, saflufenacil, metribuzin, or dicamba to glufosinate, b) increasing the rate of glufosinate from 500 to 1000 g ai ha−1, and c) the addition of 28% urea ammonium nitrate (UAN) as the carrier solution. Across a two-year period (2020–2021), four field trials were conducted on commercial farms located in southwestern Ontario, Canada, with confirmed GR horseweed. Glufosinate controlled GR horseweed 65, 66, and 63% at 2, 4, and 8 weeks after application (WAA), respectively, and reduced density and biomass 46 and 33% at 8 WAA, respectively. There was no improvement in GR horseweed control from the addition of halauxifen-methyl, 2,4-D ester or saflufenacil to glufosinate and no decrease in density and biomass with the exception that the addition of saflufenacil to glufosinate reduced density 30% compared to glufosinate alone. The addition of metribuzin to glufosinate improved GR horseweed control by 22, 22, and 28% at 2, 4, and 8 WAA, respectively, and further reduced density and biomass 50 and 47%, respectively at 8 WAA, respectively. The addition of dicamba to glufosinate improved GR horseweed control by 19, 26, and 30% at 2, 4, and 8 WAA, respectively, and further reduced density and biomass 54 and 60%, respectively at 8 WAA. There was no improvement in GR horseweed control by increasing the rate of glufosinate from 500 to 1000 g ai ha−1 and or when using 28% UAN as the carrier solution. The addition of all herbicides to glufosinate, increasing the rate of glufosinate, or using 28% UAN as the carrier solution improved the consistency of GR horseweed control.