Are you looking for a crunchy pickle or a soft vegetable? I'm not sure if I've ever seen cauliflower preserved in oil, but I know you can make giardiniera -- a vegetable mix including chopped cauliflower, preserved in vinegar. You might have to cook the cauliflower (blanch it, at least) before packing it in whatever brine or vinegar solution. But that could give you a relatively crunchy veg.
If you are set on oil, maybe you can "confit" it -- long, slow poach in oil with chilies and garlic. I've never tried that, but :look: hmmm, maybe????? In any case, I would not try to keep raw cauliflower in oil; it strikes me as potentially dangerous, just like raw garlic in oil.
I agree with Suzanne. I don't think it would work that well, and there's a danger factor with the oil going rancid, etc. A pickled version...sure. Delicious! No problems there. Make sure you process your jars properly.