Shares in outdoor advertising group QMS Media surged more than 23 per cent on Tuesday after confirmation that private equity group Quadrant had made a cash bid valuing it at more than $420 million.

The QMS board has said it will back the $1.22 a share bid, plus a 1.3c final dividend, in the absence of a superior offer and subject to an independent expert concluding that the deal is in the best interests of shareholders.

Shares which had been trading at 90c last week - before takeover speculation emerged - rose 23.5 per cent to $1.235 on Tuesday.

"Having fully considered a range of strategic alternatives in relation to some or all parts of the QMS business, including the receipt of an unsolicited proposal from Quadrant, the board believes this offer allows QMS shareholders to realise significant value for their shares," said QMS chairman Wayne Stevenson.