The Nigerian rushed to west London on the final day of the January transfer window yesterday despite the two clubs having failed to reach an agreement over a deal.
"Peter has acted wholly unprofessionally. He must now accept the fact he remains under contract for a further 18 months and has to focus on his Albion commitments," West Brom chairman Jeremy Peace said on the club's website (www.wba.co.uk).
The 31-year-old striker, who joined West Brom in 2010, handed in a transfer request a week ago, which the club rejected.
West Brom, who said yesterday they had turned down a second bid for the forward and, had repeatedly said they had no need or desire to sell their core players.
"The only way we would have considered letting Peter leave was if an acceptable offer was forthcoming and if we had found a suitable replacement at relatively short notice," Peace said.
"Neither materialised and, in the end, the matter became a point of principle as much as anything."
West Brom said they had never given Odemwingie permission to speak to QPR about a potential move, while QPR manager Harry Redknapp put the situation down to a "mix-up".
"I feel sorry for the lad and the way the whole thing's turned out," Redknapp told Sky Sports News.
"It wasn't any of our doing. I think he was maybe advised that he should turn up here and that the club had made an offer and the offer had been accepted. The wires got crossed somewhere."
West Brom will hope Odemwingie can put all thoughts of the past week out of his mind and concentrate on club matters, starting on Sunday when ninth-placed Albion host fourth-placed Tottenham Hotspur in the Premier League.