The Catalan giants are now three games away from becoming the first side to go all term without losing a match in the Spanish top flight since the 1930s after passing the toughest of their remaining tests.
Barca were pegged back in the first half before having Sergi Roberto sent off, and it was a similar story in the second as Gareth Bale struck to cancel out Lionel Messi's latest El Clasico goal in an entertaining match.
Before the first half spiralled out of control, with three yellows and a red being dished out in quick succession, both sides created a few chances in an evenly-contested affair.
Barca started the better, slipping through Luis Suarez who was denied by an impressive Raphael Varane block, before the Uruguayan striker volleyed home from the next attack after Roberto picked him out perfectly from eight yards.
Madrid had been second best up until that point and had struggled to get the ball forward, but that all changed once levelling up through a Ronaldo goal on the counter.
A move that started deep inside their own half culminated in Karim Benzema heading Toni Kroos's cross back across the target for Ronaldo to convert from under the crossbar.
Ronaldo was then wayward with a couple of headed attempts as control of the game swung the visitors' way, as they attempted to make it four games without defeat on enemy territory.
Barca were starting to be pulled apart as the half went on, with Ronaldo being played behind on a couple of occasions, only to be denied by Marc-Andre ter Stegen and then sending the second of the chances wide of goal.
The match had threatened to boil over as half time approached following a series of nasty challenges and, after Jordi Alba and Bale escaped any action for possible red-card offences, Roberto proved less fortunate as his slap on Marcelo was spotted by the officials.
Madrid, without star man Ronaldo for the second half, were behind within seven minutes of the restart as Messi took the ball past two men and tucked it out of Navas's reach, moments after Marco Asensio sent a shot right at Ter Stegen.
Visiting players were unhappy with the referee, however, as Suarez kicked the back of Varane's leg before feeding the ball to Messi inside the box to do the rest.
Messi was denied a second goal by a smart Keylor Navas stop 20 minutes from time, and that would prove a big moment as Bale put enough spin on his first-time shot from the edge of the area to help it past Ter Stegen.
Perhaps due to tiredness, Barca had dropped deep in the build-up to Bale's second-ever El Clasico goal and Madrid were looking the more likely to win the contest as the last 15 minutes arrived.
A big decision also went against Los Blancos when the referee opted against pointing to the spot after Alba caught the legs of Marcelo inside the area.
Messi, now with 26 El Clasico goals to his name, was desperate to add another to his tally, bending a shot wide and then testing Navas at his near post.
Neither side was willing to accept a point as the final throes approached, but in the end a point apiece was just about the right outcome.
BARCELONA (4-3-3): Ter Stegen; Roberto, Pique, Umtiti, Alba; Rakitic, Busquets, Iniesta (Paulinho 58'); Coutinho (Semedo 46'), L.Suarez (Alcacer 92'), Messi
REAL MADRID (4-3-3): Navas; Nacho (Vazquez 68'), Varane, Ramos, Marcelo; Modric, Casemiro, Kroos (Kovacic 84'); Bale, Benzema, Ronaldo (Asensio 46')