Cristiano Ronaldo and, in a more unlikely turn of events, Nacho, also notched doubles to boost under-fire boss Zinedine Zidane.
Loses to Barcelona and Villarreal either side of the mid-season break contributed to leaving Madrid fourth and 19 points off the pace in the title race, and further woes awaited when Adrian Lopez capitalised on slack defending to net a 23rd-minute opener.
Amid palpable unrest from the stands, Madrid steadied themselves and centre-back Nacho levelled, before Bale took centre stage.
The Wales star finished exquisitely to give Zidane's men the lead at the break and he converted Toni Kroos' corner before the hour to make the points safe.
That Bale is now Madrid's joint-top scorer in LaLiga with six this season owes much to Ronaldo's trials in front of goal.
Those were again gruesomely evident until the five-time Ballon d'Or winner followed Luka Modric onto the scoresheet 12 minutes from time and his brave diving header preceded Nacho completing a rout that leaves Deportivo slumped in the relegation zone.
Borja Mayoral was preferred in attack alongside Ronaldo and Bale by Zidane and the 20-year-old forward turned Modric's cross goalwards to draw a fifth-minute stop from Ruben Martinez in the Deportivo goal.
Madrid largely ambled through the opening exchanges, with nothing to show for their meagre efforts, and the Bernabeu faithful whistled their side when they fell behind.
Florin Andone's clever flick on caught out Dani Carvajal and Lucas Perez scooted past a napping Raphael Varane for Adrian to slide home.
Marcelo was the closest player to the Deportivo goalscorer and, seemingly stung, the left-back drove an impressive response from the hosts.
He saw an angled volley flash wide before Ruben brilliantly saved a Ronaldo header from the Brazil international's 28th-minute cross.
Ruben then fortuitously turned a Marcelo drive on to the base of his post and it was no surprise to see him turn provider as Nacho steered home in assured fashion.
Madrid kept their momentum rumbling on and were rewarded three minutes before half-time.
Ronaldo went to ground under minimal encouragement from Depor defender Fabian Schar and, as he berated the referee, Bale collected the loose ball from Marcelo's cross and curled a sumptuous strike into the top corner.
Five minutes into the second half, Ronaldo contrived to foul Schar as Carvajal's low ball across the box suggested a tap-in.
A sliding Mayoral was unable to provide the decisive touch at the end of Marcelo's latest raid and, in another recurring theme of the match, Ruben showed lightning reactions in the 58th minute to deny Casemiro from Kroos' cross.
Kroos trotted over to the left flank to take the resulting corner when Bale rose unchallenged to muscularly power home the header.
Mayoral headed a Bale cross off target from four yards and that miss heralded the introduction of Karim Benzema, a substitution that was whistled by a section of supporters apparently underwhelmed by the long-awaited reunion of the BBC.
Ronaldo had a contribution to enjoy as his 68th-minute backheel teed up Modric to crisply net his first league goal of the season from the edge of the box.
Andone should have pulled one back from close range for Deportivo before Ronaldo controlled brilliantly with his chest, only to finish with all the poise of a rank amateur.
There was relief and a notable lack of his trademark celebration when Ronaldo finished Casemiro's cross from close range.
He joined Bale with a double but paid a painful price in the 84th minute, bloodied by Schar's boot as he bravely converted a centre from substitute Lucas Vazquez.
Nacho suffered far less for his own satisfaction, converting a set-piece against opponents who appeared to have clocked off before the final whistle.
