A barley cultivar, designated YU599-012, is disclosed. The invention relates to the seeds of barley cultivar YU599-012, to the plants of barley YU599-012, and to methods for producing a barley plant produced by crossing barley cultivar YU599-012 with itself or another barley variety. The invention also relates to methods for producing a barley plant containing in its genetic material one or more transgenes and to the transgenic barley plants and plant parts produced by those methods. The invention also relates to barley varieties or breeding varieties and plant parts derived from barley cultivar YU599-012, to methods for producing other barley varieties, lines or plant parts derived from barley cultivar YU599-012, and to the barley plants, varieties, and their parts derived from the use of those methods. The invention further relates to hybrid barley seeds and plants produced by crossing barley cultivar YU599-012 with another barley cultivar. This invention further relates to methods for developing other barley varieties or breeding lines derived from variety YU599-012 including cell and tissue culture, haploid systems, mutagenesis, and transgenic derived lines. YU599-012 demonstrates a unique combination of traits for the human food market including waxy starch, hulless seed and increased levels of Beta-glucan fiber and Beta-glucan fiber viscosity.