Valanciunas made the first of two free throws with 0.1 seconds remaining after he was fouled by Clint Capela under the Grizzlies basket. The clock ran out after Valanciunas, who also had 15 rebounds, missed the second foul shot.
Harden scored 15 during a 17-2 fourth-quarter burst that helped the Rockets tie the game at 115 at the end of regulation. Harden’s three free throws with 4 seconds left tied it.
Conley ended the night 12-of-23 from the field, including 6-for-9 from outside the 3-point arc. Valanciunas made 10 of 19 shots from the floor and was 13-of-17 at the foul line.
Harden, who added eight assists, scored 28 points in the fourth quarter and overtime.
Harden had previously scored 57 against the Grizzlies on Jan. 14. He’s the third player to record multiple 50-point games against one opponent in a season over the past 30 seasons, joining Kobe Bryant and Michael Jordan.
It was also his seventh 50-point game of the season, and he became the second player in NBA history to record a 50-point game in five straight months, joining Wilt Chamberlain.
Chris Paul had 18 points and seven assists for Houston, which had won three straight. Capela added 14 points and 10 rebounds.
Grizzlies: Heisman Trophy-winning quarterback Johnny Manziel, signed recently by the Memphis Express of the Alliance of American Football, attended the game. … Memphis was already dealing with numerous injuries to key players when earlier this week CJ Miles was declared out for the season with a stress reaction to his left foot. Avery Bradley was ruled out Wednesday with a bruised right shin. The team will re-evaluate the injury in a week. … With Bradley out, Delon Wright started his third game since joining Memphis at the trade deadline. … Conley has scored at least 20 points in six straight games, matching the longest such streak of his career.
Rockets: Host the San Antonio Spurs on Friday.
Grizzlies: At the Orlando Magic on Friday.
The Associated Press contributed to this report.