The 67-year-old took over at Loftus Road in 2012 but could not prevent the west London club sliding to Barclays Premier League relegation.
Although they were installed as favourites to seal an immediate return, poor form around Christmas saw Redknapp's side having to negotiate the play-offs to gain promotion.
And it was during the play-off final win over Derby when Redknapp started to face the prospect of walking away - only for Bobby Zamora to score a last-gasp winner.
"If we hadn't gone up this year I would have turned it in," he conceded.
"I would have definitely packed up. I wouldn't have gone back and done another year in the Championship, it didn't appeal to me any more.
"If we had got beat I would have turned it in, definitely.
"With 10 minutes to go I was thinking 'what golf club should I join this year - should I play here or there?' and then suddenly Bobby ruined it all."
Zamora's strike secured a top-flight return and Redknapp is glad to still be at the helm as he looks to help the R's flourish in the Premier League this time around - with a troublesome knee also no longer causing him problems.
"Now I am excited again," he said.
"To go to Anfield and Old Trafford is fantastic, I am so lucky to be able to do that.
"I wouldn't have missed the Championship. I didn't fancy it. I would have said 'let somebody else have a go for a year' because I like the people here - I like the chairman, I genuinely look forward to seeing him.
"My leg is a lot better. I was struggling last year. I didn't need an operation in the end, I just got on the bike and strengthened it.
"I thought I would be out for three months with an operation - but the Premier League is exciting and I am looking forward to it."
With former England and Manchester United captain Rio Ferdinand the only new recruit so far, Redknapp will be wanting to add more to his squad before the season opener at home to Hull.
"We'll get them in, we know that," he said.
"I'm not making it up. A couple of boys are training with us who are not with us and we have Adel (Taarabt), who looks like he's going to go.
"I've got a couple of kids playing with us to make up the numbers. We've got around 12, with a couple to come back. We'll be a maximum of 13 or 14."