Overlooked means to not notice, not consider or not pay attention too. Example: I overlooked my homework. Missed out is used when talking about a goal or doing something. Example: I missed out on the chance of seeing my favourite band.

Overlook means- 1."fail to notice or consider" 2."Ignore or disregard " e.g "she overlooks his faults". Missed Out-Leave out or Omit e.g An important fact had been missed out