Oyeleke’s strike from inside the box smashed against the post before hitting former Spireite Grant Smith on its way in.
Kabongo Tshimanga doubled the lead in the first-half after latching onto a long ball by Scott Loach.
The win takes Chesterfield top of the National League and extends their unbeaten run to seven games.
Here are Liam Norcliffe’s player ratings from the match at Huish Park...
1. Scott Loach 7
A fifth clean sheet in seven games. Assisted the second goal when his long kick ran all the way through to Tshimanga to score. Made one or two fairly comfortable saves in the second-half. Dropped a corner delivery which was bundled in during the first-half but the referee awarded a foul in his favour. Grimes got him out of jail when clearing one off the line after he initially came rushing out before retreating. Photo: Tina Jenner
2. Fraser Kerr 7
Went about his business with minimal fuss as always. Did the basics well. Photo: Tina Jenner
3. Gavin Gunning 8
He was a rock, epsecially considering he broke his nose early on. He was dominant in the air and mopped up at the back. Such is the warrior that he is he continued until half-time. Photo: Tina Jenner
4. Jamie Grimes 7
Made a crucial clearance off the line moments before Chesterfield went 2-0 up. He was in strong in the air. He went to ground a bit too easy with one or two tackles in the second-half. Might have done better in possession at times but in general he was more than fine. Photo: Tina Jenner