For pickled oil peppers, bring vinegar and oil to a boil. Add onions, garlic and all other spices except horseradish and cook briefly.
Put the whole peppers in the vinegar and let them bubble a few times.
Place the peppers in jars, add the horseradish and fill with hot vinegar.
The peppers must be covered to the height of a finger. Close the jars. Pickled oil peppers are best kept in a cool place.