of course
off on the wrong foot
off the cuff
off the hook
off the record
old habits die hard
old hat
old school
on a roll
on a silver platter
on a tear
on cue
on demand
on doorstep
on edge
on one’s uppers
on pins and needles
on the back burner
on the ball
on the brink of
on the cards
on the case
on the crest of a wave
on the dot
on the drawing board
on the horizon
on the mend
on the other hand
on the rocks
on the run
on the same page
on the tip of my tongue
on top of something
on top of the world
on track
on view
on your bike
on your last legs
on your mark
once bitten, twice shy
once in a blue moon
one cannot love and be wise
one sandwich short of a picnic
one stop shop
other half
BROWSE IDIOMS THAT START WITH LETTER "o"
A list of idioms in alphabetical order with definitions and examples