Morecambe’s poor run of form continued after a nightmare first-half helped Oxford claim the three points.
The Shrimps’ woes in the opening 45 minutes continued as they were three goals down at the break at the Kassam Stadium.
The warning signs were there when James Constable missed a golden chance on three minutes when he failed to find the target from six yards out after a mistake by Stewart Drummond.
But he was on target on 15 minutes from close range when he bundled home the loose ball after Barry Roche had saved well from Dave Kitson’s close-range header.
Nine minutes later the home side doubled their advantage when the Shrimps were caught out at the back after Tony Diagne’s wayward pass on the halfway line. Oxford broke quickly through Ryan Williams and his low cross was bundled home at the back post by the on-rushing Sean Rigg.
There was worse to follow for Morecambe when the offside looking Williams broke free again down the right after the visitors had given the ball away and he kept his cool to lob the ball over Roche and over the line despite the best efforts of Andy Parrish.
Morecambe’s only threat of note came in the early stages of the game when Kevin Ellison saw a shot deflected over the bar after being played behind the home defence.
The Shrimps were much brighter in the second half and created several chances.
Ryan Williams and Andy Fleming both tested home keeper Clarke from distance before Jack Sampson hit the post with a sweetly struck low shot from just inside the box.
The pressure continued with Diagne seeing a shot beaten down as the Shrimps restricted Oxford to just one clear chance when Rigg was played in on goal but denied by a fine save from Roche.
Oxford: Clarke, Hunt, Raynes, Mullins, Newey, Williams (Davies 86), Rose, Hall, Rigg (O’Dowda 66), Constable, Kitson (Marsh 88). Subs not used: Crocombe, Long, Bevans, Ruffels.
Morecambe: Roche, Wright, Parrish (McCready 85), Hughes, Diagne, Drummond, Fleming, Williams, Amond, Sampson (Marshall 62), Ellison (Redshaw 77). Subs not used: Arestidou, Threlfall, Kenyon, Mwasile.
Referee: Garry Sutton.