Danny Murphy's penalty along with efforts from Clint Dempsey and Bobby Zamora complemented Johnson's treble.
Fulham manager Martin Jol was delighted with his team's performance.
"We took the initiative," he said. "Sometimes you need to let them play to get more space for our four attacking players and we did well in that respect.
"We played 4-4-2 today [Sunday] with two wide players who could come in. That caused them a problem with the full-backs overlapping as well, especially John Arne Riise.
"But don't forget that we've done that before.
"It's not the first time - I've been here for four months.
"The only thing we did differently was Moussa Dembele played instead of Damien Duff and he's a very gifted player."
Johnson was the standout player just days after netting twice in Fulham's 2-0 Europa League victory over Odense BK.
While Jol was quick to praise the frontman, the Dutchman was impressed with the team effort.
"I'm very happy for him and for us as well," he said.
"He scored the goals in Europe, did it in the Premier League but it doesn't matter who scores the goals, we need the results.
"I felt that maybe today we scored too many but on other days we didn't get the goals we needed.
"I felt like we did the same [today] as we have done before. We just couldn't put the ball in the net. It's not about blaming the strikers, it's a normal conclusion."
Johnson's contract runs out at the end of the season and asked over progress on a new deal, he added: "Other people are doing the negotiations.
"I will back him all the time and hopefully he is good for us this season because he has scored more goals today than he did in the whole of last season.
"But I feel Andy Johnson and Fulham is a good combination."
The Dutchman also commented on reports that surfaced suggesting that he has fallen out with striker Zamora.
"There are agents," he said. "If you drop somebody or leave someone out they will tell their agent and the agent will tell you [the press].
"Bobby is okay. He is a sensitive person.
"Sometime you leave him out but if he's ill in bed you can't expect me to take him with us.
"He was ill. He was not even on the training ground.
"When he came to training I said 'you better stay here and do some extra sessions'.
"I still had Andy Johnson and he proved me right up front because he scored two goals."
Warnock's miserable afternoon was compounded further by suggestions that playmaker Taarabt stormed out of Craven Cottage after being substituted.
Asked about the situation, he said: "That's not my problem at the moment. I have no idea [whether he left the dressing room].
"I've more worries than any individual when you lose 6-0.
"I don't think you can blame Adel Taarabt today," he continued. "We conceded six goals. You've got to look at that.
"If I'm honest, if we had Darren Bent playing for us today, and a few England players, we'd have still been beaten 6-0.
"I don't think you can get carried away too much. You get days when Adel comes off. You're going to get days when he throws his toys out the pram, but that isn't a worry for me.
"If I sub somebody and they are happy, then I have more of a problem with that."
Asked again whether he knew if Taarabt was at the stadium for the second half, Warnock retorted: "I'm not concerned about that.
"You can make whatever you want from the situation."
After being asked once more about Taarabt, Warnock walked out the post-match press conference.
QPR refused to comment on the speculation when contacted by Press Association Sport.
By coincidence, Taarabt was recalled to the Morocco squad earlier on Sunday three months after walking out on the team and vowing never to play international football again.
While the Hoops endured a difficult day against their near neighbours,