The present invention relates to a Lactuca sativa seed designated 79-504 RZ, which may exhibit a combination of traits including resistance against downy mildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae), currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, and lettuce mosaic virus (LMV), as well as an extraordinary high number of substantially equally sized leaves, which leaves are medium green, slightly to moderately blistered, and have a slightly to moderately undulated apical leaf margin, which is shallowly dentate. The present invention also relates to a Lactuca sativa plant produced by growing the 79-504 RZ seed. The invention further relates to methods for producing the lettuce cultivar, represented by lettuce variety 79-504 RZ.