Dowie was sacked in February by Ray Ranson and will take over the club which will have plenty of money to spend thanks to a new board which includes F1 boss Bernie Ecclestone.
"I'm privileged to have been given the opportunity under the new ownership to return to the club where I served my managerial apprenticeship," said Dowie who played for QPR for three years to the BBC.
"This is a very exciting long-term project and 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."