More than 100 million Americans are expected to travel during the holidays, and many will search for lodging online. But travelers may unknowingly pay more and fail to see all of their options because some major hotels have ganged up with Google to undercut competition.

Online travel agencies like Expedia, Priceline and Travelocity have replaced brick-and-mortar agents by offering consumers more choice and convenience at a lower price. These OTAs purchase inventory from wholesalers and then market rooms at a discount to consumers...