The visitors on Saturday built a 3-0 lead at Balaidos Municipal Stadium in this northwestern city thanks to an early goal set up by Bale and finished off by Karim Benzema, a spectacular strike by Toni Kroos at the one-hour mark and a late score by Lucas Vazquez, who had come on as a substitute, reports Efe news.
But Real Madrid also relied on an outstanding defensive effort and the rock-solid play of Thibaut Courtois between the posts to secure the three points following star midfielder Luka Modric's straight red card in the 55th minute.
The visitors controlled possession just 43 per cent of the time but they managed to create more opportunities and were more effective in the opposing area.
That superiority was evident in just the 11th minute when Bale maneuvered around a defender on the left side and sent in a cross that Benzema, who was trailing the play, poked into the back of the net from close range.
Both teams then had good chances to score over the remainder of the first half.
At the half-hour mark an outstanding pass from Celta's Iago Aspas could have led to a goal, but Gabriel "Toro" Fernandez moved too slowly to the ball and allowed Real Madrid defender Raphael Varane to break up the play.
Real Madrid then had a chance to add to their lead just before the intermission but were denied by goalkeeper Ruben Blanco, who got his hand on a delicate attempt by Modric and then made a diving save of a cross-shot by Bale.
On the final play before halftime, an apparent goal by Celta Vigo's Brais Mendez was disallowed for offside after a VAR review showed that Aspas was too far forward.
The second half then began with a flurry of action, with referee Javier Estrada Fernandez sending off Modric for stomping on Denis Suarez from behind and Courtois and Blanco making remarkable saves to deny attempts by Celta's Nestor Araujo and Benzema, respectively.
There was nothing Blanco could do, however, to stop a rising missile off the foot of Kroos in minute 61, the ball ricocheting off the crossbar and over the goal line.
Celta did little with their possession advantage over the remainder of the contest, falling further behind on a goal by Vazquez in the 79th minute.
With the game well out of reach, 18-year-old youth-academy product Iker Losada finally got the home side on the board when he beat Courtois with a cross-shot in the 91st minute, three minutes after entering the game in place of Fernandez.
The story of the match though was Bale, who got the start in part because newly acquired star forward Eden Hazard was unavailable due to a thigh injury and made the most of that chance.
"Before the game we talked two or three times to say that he's going to stay. With the game Gareth had, now we just need to think about the season. I think he and everyone else now are thinking about playing and staying," Zidane said afterward.
The head coach had indicated in the offseason that Bale was not being factored into Real Madrid's plans for 2019-2020.
The Welshman had missed several friendlies after his expected move to Chinese club Jiangsu Suning fell through when the transfer deal was blocked by Real Madrid President Florentino Perez.
( With inputs from IANS )