The 43-year-old, who spent three years with Rangers as a player and also had stints as caretaker boss and assistant manager, has signed a two-year contract at Loftus Road.
"This is a very exciting long-term project," said Dowie.
"I'm very privileged to have been given the opportunity under the new ownership to return to the club where I served my managerial apprenticeship.
"I've been thoroughly impressed by the new investors and their fresh, aggressive and innovative approach to all sporting matters, as well as the marketing and commercial aspect of this football club.
"QPR is a fantastic club, with a successful history and I'm going to relish the challenge that lies ahead."