The initial idioms of the letter O

onward and upward	onward
onwards and upwards	Onwards and upwards!
oodles	oof
oomph	OOSOOM
ooze with	ooze
OP	OP’s
open	open (one's) big mouth
open (one's) legs	open (up) a can of whoop ass (on someone)
open a can of worms	open a conversation
open a few doors	open a Pandora's box
open and aboveboard	open and shut
open day	open doors
open eyes	open eyes to
open fire	open for business
open heart	open heart to