I don't have an article specifically talking about horror being overlooked at the Oscars, but I have mentioned it many times in other articles discussing the Oscars. There are several films, including Frankenstein (1931), Psycho (1960), The Innocents (1961), Night of the Living Dead (1968), Don't Look Now (1973), The Exorcist (1973), Carrie (1976), Alien (1979), The Shining (1980), The Babadook (2014), Get Out (2017), and various others that have been criminally overlooked (at either nomination or winning stages).
However, I can offer this piece, as even if you've seen all the films listed, there are links in the article to other lists I've compiled in specific horror subgenres. I hope that helps. :)