Let me start by saying there is no such word as "oxymorons". The plural of oxymoron is "oxymora". More importantly, to be truly an oxymoron, an expression must be a combination for epigrammatic effect (that is, a terse, sage, or witty often paradoxical saying) of contradictory or incongruous words (as cruel kindness, laborious idleness).
Most expressions commonly cited as oxymora are, in fact "perceived oxymora" or "joke oxymora" because they don't precisely fit the definition of oxymoron. If there is a sense in which the words properly complement each other, then though the words can be perceived as an oxymoron, they are not truly an oxymoron. Example: Jumbo Shrimp. This is often perceived as an oxymoron because "jumbo" means big, and "shrimp" means little. But the intended meaning of the words are "large" and "crustacean", respectively. Not at all a contradiction. I've never heard of the use of "jumbo shrimp" to call something both large and small at the same time in a sage, witty, or paradoxical way, but I'm willing to be corrected. The "joke oxymora" include such expressions as "military intelligence", "Microsoft works", etc. which are supposed to be funny because of the reputation of the entities involved.
Here is a small sample of oxymora, perceived oxymora, and joke oxymora. See if you can see which is which. Check the Internet reference at the end of this article for a more complete list.
Baby grand piano
"Now, then ..."
Synthetic natural gas
Temporary tax increase
Microsoft Works, Government Works, etc.
Wikipedia: List of oxymorons
Go back to Constructions, further back to Structure, or all the way back to Language