Oh made the cut on the number, a final hole birdie in round two proving crucial as she signed for a 3-under 69 to get to 1-under for the first 36 holes and sneak into the weekend.
Oh and Katherine Kirk are the only Australians through to the final 36, the other five who teed off Thursday all failing to qualify.
Oh finished several hours ahead of the final groups and watched nervously as the cut line drifted between 1-under and 2-under as rain pelted the afternoon field.
Eventually, 1-under was good enough for T65 and Oh took her place among the 77 players who will play the last two rounds.
Kirk also signed for a 3-under 69 and is one shot ahead of Oh at 2-under for the week, nine behind leader In Kyung Kim who added a 4-under 68 to her opening 65 to lead by two shots.
England’s Georgia Hall and World Number Two Lexi Thompson share second place at 9-under.
Seven Australians began the week but with only Whitney Hillier breaking par on day one it was always going to be a difficult assignment with the cut coming in red figures.
Australia’s highest ranked player, Minjee Lee, signed for a 73 to be 1-over for the week and miss by two, Sarah Jane Smith on the same total despite a second round 70.
Hillier bowed out after a second round 75 dropped her to plus two, a disappointing result after such an impressive opening round.
Stacy Peters survived qualifying to earn her place in the field but 74-73 added up to four too many, Karrie Webb also finishing at 3-over after scores of 75-72.
Both Oh and Kirk will need something special over the weekend to contend but the Kingsbarns course has already shown the volatile nature of links golf.
Kirk’s round typified the agony and ecstasy of this form of the game with six birdies on her card all but ruined by a disastrous triple bogey six at the par-3 14th.
Oh also managed six birdies on day two but dropped three shots along the way.