Reid has made just 10 appearances for Blackburn this term following his recovery from a long-term injury and his contract expires in the summer.
The Republic of Ireland international, who turns 29 next week, is happy to have linked up with West Brom and aims to rediscover his best form during his time with the promotion hopefuls.
Exciting time
"It's been a busy couple of days," Reid told the club's official website. "When I found out I was going out on loan this was one of the clubs I would like to have joined.
"The manager at Blackburn has said there is still a part for me to play there, but now I'm fully focused on doing the job at West Brom and it's an exciting time for me and the club.
"My contract is up in June, so this isn't just a chill out. This is a big move for me.
"I've got a lot to prove to a lot of people, and to myself, that I can get back to my best. I've got no doubt I can do that.
"I just want to rediscover my best form and there's no reason, if I can have a good month here, why it couldn't be extended even longer.
"And, with my contract up in June, who knows? It's a big opportunity this month, starting today."
Q.P.R. v West Brom Correct Score: West Brom 2-1 15/2
Source: Team Talk
Source: Team Talk