‘FLLA09015‐U1’ (Reg. no. CV‐387, PI 699117) is a new facultative oat (Avena sativa L.) cultivar that was co‐developed by the University of Florida and Louisiana State University Agricultural Center and was released in 2019. This line was derived from a single cross of FL0210‐J1/MN06203. FLLA09015‐U1 has considerable potential for grain and forage yield and for conservation tillage purposes in the southern United States. Exclusive marketing rights for FLLA09015‐U1 has been granted to JoMar Seeds and is currently commercialized under the name of Juggernaut. FLLA09015‐U1 was developed using selected bulk breeding method and was selected as an F5:6 head row. The line was evaluated in advanced, regional, and state grain and forage yield trials from 2015 to 2021. FLLA09015‐U1 was observed to be uniform and stable across environments in the southern United States from 2015 to present. The line possesses a semi‐prostrate growth habit and has large leaves that are dark green in color. It is a mid‐maturing, medium to mid‐tall height with excellent grain yield and good forage yield and test weight. It has excellent crown rust resistance and very good resistance to Barley yellow dwarf virus and stem rust and demonstrated moderate lodging resistance. It has performed very well in both grain and forage trials. FLLA09015‐U1 has broad environmental adaptation and has performed well in Louisiana, Florida, Georgia, Texas, Alabama, and South Carolina. We consider FLLA09015‐U1 to be a good dual‐purpose type of oat because of its high grain yield potential and vigorous growth and high tillering capacity. Core Ideas FLLA09015‐U1 a facultative oat cultivar that was co‐developed by the University of Florida and Louisiana State University. FLLA09015‐U1 has broad adaptation and has performed well in Louisiana, Florida, Georgia, Texas, and Alabama. FLLA09015‐U1 is a good dual‐purpose type of oat and has high grain yield potential and vigorous growth and high tillage. FLLA09015‐U1 has good crown and stem rust and Barley yellow dwarf virus resistance. FLLA09015‐U1 has considerable potential for grain, forage, conservation tillage, and wildlife use in the southern USA.