Is this parallelism/exposition/foreshadowing/or setting?
In Beowulf, the narrator says that it was not Grendel's "fate to finish the feast / he foresaw that night." Is this an example of parallelism, exposition, foreshadowing, or setting?
I'm guessing foreshadowing, but I'm pretty clueless.
I'm guessing that you're right. It's probably foreshadowing. The foreshadowing here is the narrator speaking to the audience, giving a hint of what is coming in the story. Grendel thinks that he'll be feasting on the sleeping men, but the narrator and reader both know that Beowulf is there, ready, to face down the monster. Foreshadowing can be seen a gentle hint-dropping from narrator (or author) to reader about what is going to happen as the story advances.
One way to check the answer to your question, of course, is to rule out the other possibilities. Parallelism is the use of similar elements or phrases, such as the paired prepositional phrases in "over hill and over dale." Setting is usually defined as the time and place in which a story is set. Exposition is usually defined as the place in the story (often at the very start) in which the setting and any necessary background information are given (e.g. the "crawl" of text in the opening of the first Star Wars movie).