John Sheridan’s side, cheered on by nearly 1,300 travelling fans, came close to returning to Devon with a full three points rather than just one after a Reuben Reid first-half header bounced off the bar and the post.
Striker Patrick Hoban came closest for the home team, who are now unbeaten in five games.
Next up for seventh-placed Argyle is another away match at Dagenham & Redbridge on Tuesday night (7.45pm).
Oxford United: Ryan Clarke; George Baldock, Jonny Mullins, Jake Wright, Joe Skarz; Alex MacDonald (Giorgio Rasulo 87), Mike Collins, Joe Ruffles, Kemar Roofe; Callum O’Dowda (James Roberts 72), Patrick Hoban (Armand Gnanduillet 87). Subs not used: Danny Rose, Jamie Ashdown, 22 Sam Long, Chey Dunkley.
Argyle: Luke McCormick; Curtis Nelson, Carl McHugh, Peter Hartley; Kelvin Mellor, Drew Talbot, Bobby Reid (Olly Lee 68), Anthony O’Connor, Tareiq Holmes-Dennis; Lewis Alessandra (Jason Banton 68), Reuben Reid (Ryan Brunt 82). Subs not used: James Bittner, Ben Purrington, Dominic Blizzard, Tyler Harvey.