A win at home to struggling Oster would be enough for GAIS to continue this surprise Allsvenskan campaign and reach Europe.
Midway through the first half at Gamla Ullevi, Ibrahim Diabate contested a ball over the top, which fell to Rasmus Niklasson - he brought it down well and cleverly squared it back to Diabate, who rifled it into the top corner from the edge of the area to put the hosts in front.
But Oster, fighting for their lives, were not about to let GAIS stroll to victory, and five minutes before the break they were level when a low ball from Noah Soderberg was not dealt with by the defence, and Daniel Ljung was on hand to place it into the bottom corner.
In the second half, the Mackerels put the visitors under constant bombardment, having 72% possession and taking 23 shots, but only one of those 23 was on target - a Robin Wendin effort that was dealt with by Robin Wallinder in the Oster goal.
With seconds to play, Gustav Lundgren was through on goal and certain to at least hit the target, but a rash challenge just outside the area from Mattis Adolfsson stopped him in his tracks and earned the defender a straight red card.
The 1-1 draw moves Oster back into the Relegation Playoff Place ahead of Degerfors on goal difference, but their survival rival has a game in hand.
In the race for Europe, the point made for an anxious wait for GAIS, but eventually they could celebrate knowing that Djurgarden had drawn 0-0 with IFK Goteborg.
A win for Goteborg would take the fight against the side they share a stadium with to the final day, but in the first half, the Gothenburg side were happy to still be level, after an incredible double-save from Elis Bishesari to deny August Priske at point-blank range.
Midway through the second half, the Goteborg task became greater when a clumsy challenge from Rockson Yeboah saw the visitors reduced to 10 men, but Djurgarden failed to take advantage and the game ended goalless.
That meant Goteborg remained four points behind GAIS, but now with only three points to play for, while Djurgarden sit a place and two points further back, as their European hopes were ended by GAIS' point.
Goteborg and Djurgarden both dropped a place this weekend, as moving up to fourth are AIK, but their 3-0 win over Elfsborg proved too little too late, as they also find themselves four points behind GAIS.
Erik Flataker's header gave AIK the lead after 13 minutes, before two Johan Hove efforts - a deflected strike from range and an injury-time penalty, rounded off the victory.
A disappointing second half of the season sees Elfsborg finish in eighth, but that didn't spoil the tributes in Boras to the outgoing Johan Larsson, who is leaving the club after more than 350 appearances across spells at the start and finish of his career.
A goalless draw between Halmstad and Brommapojkarna ensured survival for the hosts, while Oster's failure to win later on Sunday meant BP had secured their top-flight status for 2026.
On Saturday, a late Simon Gustafson equaliser cancelled out Hugo Bolin's first-half goal as Hacken and Malmo drew 1-1. Hacken stay 10th, while Malmo could still rise from seventh to fourth, but there will be no European football for MFF next year.
Tim Prica's goal in stoppage time was not enough for Norrkoping, who fell to a 2-1 home loss to Sirius after goals from Joakim Persson and Leo Walta early in the second half. It's five losses in a row for Norrkoping, who are three points above Oster and thus not safe going into the final day.
Follow the Allsvenskan final-day survival battle on Flashscore.
