1987 Tor BooksThe second novel in the series, The Sound of Midnight (1978), we get a young woman on fire - flames were popular post-Audrey Rose - and another reference to a bestselling King novel. Now Charles gets his first name on the cover!
1979 Popular Library
1987 Tor BooksThe ever-present King blurb now on a Nancy Drew-ish cover for The Last Call of Mourning (1979). I like the Tor edition, with a woman looking - expectantly? - out into the night and the growing fog...
1980 Fawcett Popular Library 
1988 Tor Books
The Grave (1981) is a reductionist horror title if I ever heard one! Note the name on the tombstone of the Tor edition.
1981 Popular Library
1988 Tor Books
1982 Fawcett Popular Library
1989 Tor Books
From my research it seems that Nightmare Seasons (1982) was the first Oxrun title that Tor published, though it was the sixth in series; we can assume this was the beginning of that stylized cover art. This one is actually a collection of several novellas set in Oxrun Station. The next book was The Orchard (1986), also a collection of novellas, which I read last year and reviewed here.
1983 Tor BooksAnd we start to move out of the vintage horror era with the two last books in the series, Tor's Dialing the Wind (1989) and The Black Carousel (1994), the latter boasting of Grant's "X-Files" novelizations. Can anyone explain why his middle initial would be excised?
These final three titles seem like a treat: Grant haunted his fictional town with the Universal Monsters! These first came out in hardcover from long-time specialty genre publisher Donald M. Grant, and then in paperback by Berkley Books. None are without a King blurb, of course. The artwork is a little on the nose for my tastes, perhaps, and Dracula doesn't look scary at all (is there perhaps a copyright on Lugosi's image?). They are: The Soft Whisper of the Dead (1982/1987), The Dark Cry of the Moon (1986/1987) and The Long Night of the Grave (1986/1988). A perpetual Halloween indeed!
