Here is a Cultural Literacy worksheet on the oxymoron as a rhetorical device. This is a half-page worksheet with a one-sentence reading, a relatively uncomplicated compound, with three comprehension questions. A simple introduction to this commonly used rhetorical move, even in everyday conversation.
If you find typos in this document, I would appreciate a notification. And, as always, if you find this material useful in your practice, I would be grateful to hear what you think of it. I seek your peer review.