Livestock primarily emits greenhouse gases (GHG) in the form of methane (CH4) from the rumen [1]. Australian feedlot industry contributed 5.8% of total GHG greenhouse gases and processing contributed another 2.1% [2]. Technologies targeting direct abatement of methane through additives have become increasingly important. Previous research has shown that bromoform, an extract of the bioactive derived from the seaweed Red Asparagopsis in a vegetable oil carrier, can reduce methane (CH4) yield of 54.5 – 95.0 % in short-fed finishers [3]. While effective in methane mitigation, its impact on cattle performance, carcass value, and cost remains uncertain, particularly under Australian commercial conditions. Understanding how red asparagopsis supplementation relates to rumen fermentation and its effect on animal performance may lead to novel strategies for reducing greenhouse gas emissions while improving animal productivity. This study evaluates red asparagopsis oil (Asp-Oil) in total mixed rations for its effect on mid-fed (150 days) beef eating quality.