The 28-year-old became the first signing after Tony Fernandes' recent takeover of the club, penning a four-year deal at Loftus Road two weeks ago.
Barton was in the final year of his contract at St James' Park and was made available for a free transfer after criticising the club's recruitment policy via his Twitter account.
Warnock admits Barton's signature was quite a coup for QPR, who could hand the midfielder his debut against the Tynesiders on Monday evening.
"It is just great to have him on board," he said.
"Whoever we're playing he will be the first on the sheet and I am sure he would want it to be like that.
"We have got a lot of players to fit in and we haven't started yet.
"We've had people out on international duty so we've had a lot of work to do but it is an exciting time.
"The players that have come in, most of them have experience at the top level and that is what I thought we lacked.
"I thought we lacked a bit of nous higher up and that is why I am delighted to have got the players I've got in.
"It wouldn't have been possible without the chairman and (vice-chairman) Amit Bhatia.
"They have both been so supportive, it is fantastic."
As well as Barton, Warnock managed to bring in five other players after Fernandes' takeover - Anton Ferdinand, Shaun Wright-Phillips, Jason Puncheon, Armand Traore and Luke Young.
The new signings will all be vying to make their debut on Monday and Warnock declared himself pleased with his last-minute deals, despite missing out on a few signings.
"We missed out on Craig [Bellamy] but in fairness to Craig he rang me at midnight and thanked me for my interest.
"It was a thing that I knew right from day one that if David N'Gog went from Liverpool, he would be going there.
"I've always liked Craig and when that didn't happen, we took a last minute gamble on Puncheon.
"It is not really a gamble, we've only got him until January so it just gives somebody else an opportunity.
"Somebody who was desperate to come. He was that desperate I didn't even know he was here until Sky Sports News picked it up. I thought it was funny that."
He added: "After the Bolton game, [Fernandes] said 'what about Scott Parker?' and I said yeah and fobbed it off really.
"It was 24 hours later when I realised he was probably serious and we made a substantial offer for Scott, but I think in the circumstances I always knew that Tottenham would have him if they came in.
"But it showed me what quality was. When he asked me for number of players, Joey Barton was top of my list before Scott.
"I had a list of midfield players and other areas, full-backs in particular.
"I gave them the list and he told me to go and get them and it was just fantastic.
"I felt sorry for the chief exec Phil Beard, who had only come on the scene that week.
"He must've wondered what hit him to be all of a sudden involved in a deadline where we are trying to sign five or six players.
"It was chaotic but I don't think we could have done much better in what we did."