The initial idioms of the letter O

off-colour	offed
offence	offend
offend against	offend with
offense	offensive
offer	offer affordance(s)
offer an olive branch (to someone)	offer for
offer one cannot refuse	offer to
offer up	offering
offer the olive branch (to someone)	Officer Friendly
officer	office
officiate	off-key
out-of-bounds	off-line
off-the-cuff	off-the-shelf
off-the-wall	OFS
often as not	often