Is there a more natural way to say this sentence in English, an idiom maybe? "Who often oversleeps might miss terrific opportunities out there."

Answer 1

I agree with Renata, The early bird gets the worm is the first idiom that came to mind. There is one more that I have heard with regard to missing out on something:

(If you) snooze, you lose.

Answer 2

Maybe this one: "The early bird catches the worm."

Answer 3

A positive take on this would be "The early bird gets the worm" - it is a very common expression and obviously creates a great visual for the benefits of getting up early and being among the first to go after an opportunity.

Another, slightly more snarky, idiom might be the simple rhyme, "You snooze, you lose" - if you are sleeping (literally or just being slow or lazy), you will miss out, especially in comparison with someone who is not!