From Die Vorzüge der Windhühner (The Advantages of Windfowl), 1956.

I started writing and drawing at an early age … My first book was a book of poetry and drawings. Invariably the first drafts of my poems combine drawings and verse, sometimes taking off from an image, sometimes from words … With drawing, I am acutely aware of creating something on a sheet of paper. It is a sensual act, which you cannot say about the act of writing. In fact, I often turn to drawing to recover from the writing.
—Günter Grass, the Art of Fiction No. 124, 1991

That “first book” Günter Grass refers to is Die Vorzüge der Windhühner (The Advantages of Windfowl), from 1956; Princeton’s Graphic Arts Collection has a few of the lithographs on their site. As Martin Esslin writes, “It is hard to tell whether the poems are there to illustrate the drawings, or the drawings to illustrate the poems”—which accords with Grass’s fairly circular description of his process. Here’s another:

Not much of Grass’s prolific visual work is available online, but Millî Reasürans, a Turkish gallery, has a few images of the disquieting engravings Grass did for his 1977 novel, The Flounder, among them this unrepentantly phallic episode:

An engraving from Der Butt (The Flounder), 1977.

There are also a few drawings from Totes Holz(Death of Wood), which Grass discusses in his Art of Fiction interview:

I have seen and drawn dying, poisoned worlds. I published a book of drawings called Death of Woodabout one such world, on the border between the Federal Republic of Germany and what was then still the German Democratic Republic. There, well in advance of the political union, a reunification of Germany occurred in the form of dying forests. This is also true of the mountain range on the border of West Germany and Czechoslovakia. It looks as if a slaughter had taken place. I drew what I saw there.

From Totes Holz (Death of Wood), 1990

John Russell wrote more broadly about Grass’s art in the New York Times in 1983:

His work relates to the ancient tradition in German art by which there is almost nothing of importance that cannot be made known to us with black ink on white paper. The marks in question may be made by cutting into blocks of wood, or with etching needle and copper plate, or with everyday pen and ink. Either way, black and white can tell us all that we need to know.