Parallel Structure and Prepositions
When prepositional phrases are used in a parallel series, prepositions (with, to, of, over, under, by, etc.) should be repeated with every element of the series unless all elements use the same preposition. A common error is to repeat prepositions unnecessarily, resulting in a stilted style.
In this sentence, there are three prepositional phrases complementing I am making a stew. If written separately and not in a single, parallel structure, they would read:
When combining these elements into a single sentence, there is no need to repeat the preposition with because it is used identically for each element.
Writing the sentence this way ensures a clear, uncluttered style.
What to Avoid: Mixing Prepositions in a Parallel Structure
Mixing prepositions improperly in a parallel structure is a common writing mistake. If a writer allows multiple phrases to share a preposition and then introduces a different preposition with another element, the result is a clumsy sentence.
If we separate the elements of this sentence, we have:
The first two elements require the preposition on, but the last element requires the preposition under. Therefore, it is necessary to repeat all three prepositions when combining the elements into a parallel sentence structure.