A goal by Tony Mowbray, his first of the season, in the third minute of extra time put Ipswich into the quarter-finals of the League Cup for the second consecutive year. Andy Legg deceived Oxford's defence by taking a short throw-in instead of launching the ball into the penalty area and nobody picked up Kieron Dyer, whose cross was headed in by Mowbray.
Legg, on loan from Birmingham, had two good chances to score in normal time. He drove a cross from Mick Stockwell wildly over the crossbar after 13 minutes and did no better from an even clearer opening seven minutes later. Jason Dozzell flicked on a Stockwell pass to the winger, who cleverly chested the ball down, but, with only goalkeeper Arjan Van Heusden to beat, his drive flew yards wide.
Ipswich, beaten 1-0 in division one at the Manor Ground last month, went ahead after 63 minutes when Dozzell headed in a Mauricio Taricco cross, and it stung United into a quick reply.
Nicky Banger muscled his way past Jason Cundy in the visitors' penalty area in the 66th minute and his square pass was touched in by Joey Beauchamp, who kept up his record of scoring in every round.
In the second period of extra time, Mowbray ensured Ipswich's victory by clearing off the line a shot by Beauchamp which had beaten goalkeeper Richard Wright and was rolling towards the unguarded goal.
Oxford Utd: Van Heusden, Gray, M Ford (Powell 96), Robinson, Purse, Gilchrist, B Ford, Smith, Banger (Murphy 96), Jemson, Beauchamp. Subs Not Used: Whitehead. Booked: Purse. Goals: Beauchamp 66.
Ipswich: Wright, Stockwell, Taricco, Williams, Mowbray, Cundy, Dyer, Holland, Mathie (Gregory 89), Dozzell, Legg. Subs Not Used: Milton, Bracey. Booked: Dozzell, Dyer, Legg. Goals: Dozzell 63, Mowbray 93.
Referee: S Mathieson (Stockport).