When the speaker says something like “Eu cozinho o jantar” I can never hear the final “o” in “cozinho”. The two “o’s” seem to run into each other as a single “o”.
Olá, @pvreed. Yes! That’s very normal. We do tend to fuse them together like that.
You can read more here about other vowels that are merged together or have their pronunciation changed in speech: Basic pronunciation: que - #4 by Joseph