The on-loan Doncaster striker, playing his sixth game, settled the nerves when he opened the scoring.
And Lee Hughes, who is almost certain to leave the Latics in next month's transfer window bagged a double to leave rock-bottom Crewe well beaten.
A delighted Byfield said: "The goal has been a long time coming and how I am hoping for a few more.
"I have been really sick during Christmas but I had a feeling that I might break my duck.
"I didn't play all that well but I was happy with the goal to help us on our way to three points.
"I haven't scored since January 1 and it is always hard to get your first for a new club. It was a big relief to see it go in."
Oldham struggled to find rhythm or tempo in the first half but took complete control after the break.
Curled
Former Jamaican international Byfield was on target in the 57th minute when his shot from eight yards left the keeper with no chance.
Then top-scorer Hughes exploded into action with two goals in 17 minutes - a curled shot after 68 minutes and a header from substitute Lewis Alessandra's superb cross.
Boss John Sheridan said: "Once we went in front I couldn't see any problems.
"It is all about winning and we played some excellent stuff in the second half.
"Even though we haven't lost in seven games now we haven't been playing all that well. But we showed some very good stuff in this one.
"I was delighted for Darren and hope it will now kick-start his loan spell with us."
Oldham host strugglers Carlisle tomorrow and Sheridan said: "They are in a false position and, although it is going to be a very hard game, I see no reason why we can't stretch our unbeaten run even further."
OLDHAM: Fleming, Eardley, Hazell, Stam (Gregan 39), Lomax, Lee (O'Grady 87), Allott, Maher, Taylor, Hughes, Byfield (Alessandra 74). Not used: Whitaker, Liddell.
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