Aristotle’s Politics Books I. III. IV. (VII.). The Text of Bekker. With an English translation by W. E. Bolland. Together with short introductory essays by A. Lang The “short introductory essays” last through page 106. (Longmans, Green, 1877). (The Internet Archive scan is dated 1887.)
Helen of Troy. (Longmans, Green, 1882; New York: Charles Scribner’s Sons, 1882.) (See also the 1913 reissue.)
Some of Lang’s ballads also cover classical subjects. See XXXII Ballades in Blue China(Kegan Paul, Trench, 1888).
The World’s Desire (Longmans, Green, 1890) with H. Rider Haggard [The Internet Archive scan of this novel given here is from 1918. A manuscript, with clear differences between Lang and Haggard’s handwriting, is preserved by the Norfolk Record Office.]
Specimens of a Translation of Theocritus. (London: [C. Whittingtham]) [Wikipedia calls this “Advance issue of extracts from Theocritus, Bion and Moschus rendered into English prose” with a date of 1879],” but WorldCat dates it [189-?]
The Iliad of Homer, a prose translation (Macmillan, 1882) with Walter Leaf and Ernest Myers. [The Internet Archive scan is from Edinburgh: R & R Clark, 1892, and notes “with corrections”.]
The Story of the Golden Fleece (Charles H. Kelly, 1903) [Juvenile Audience.] See this entry in WorldCat.
Tales of Troy and Greece (Longmans, Green, 1907) (Dedicated to H. Rider Haggard, no preface or introduction)
Tales of Troy(Longmans, Green and Co., 1910) [Longmans’ Class-Books of English Literature]
Some of the fairy books also contain Greek myths written as fairy stories.
This list was compiled using Roger Lancelyn Green’s Andrew Lang: A Critical Biography, Eleanor De Selms Langstaff’s Andrew Lang, the Andrew Lang listings in Wikipedia, and searches of Internet Archive. WorldCat was consulted when an Internet Archive scan did not exist; however, I did not check WorldCat against every entry (yet). If you are working with a particular text and are unsure of the publication date from other sources, I do recommend that you double-check WorldCat.
Please do contact me if you have any corrections or additions.