Sometimes the prefix is stressed and other times it’s not. Prefix + verb combinations usually have second syllable stress.
Here are a few examples: oversleep, overdo, understand, undertake, outlive, outperform, rewrite, redo

However, if the prefix + the root word function as a noun, the first syllable is stressed: oversight, overdose, undertaker, underwear, refill, repeat, outsourcing, outcome

With reflexive pronouns, the last syllable is stressed. Note these common examples: myself, yourself, himself, herself, itself, ourselves

Study Tip

Practice reading aloud, underlining longer words and determining syllable stress by looking in the dictionary. Your dictionary may come with an audio CD which will help you hear the correct word pronunciation.