The 30-year-old striker, who had not found the net in a league game since he grabbed a double against Lorient in December 2009, tapped the ball in from a 33rd-minute corner to put his team in front.
Ludovic Obraniak doubled the lead in the 74th minute after a superb run down the left by Benoit Tremoulinas.
"Sometimes you have to be patient and wait your turn. With the current situation at the club, I play and just try to enjoy it," said former Manchester United forward Bellion after earning only his third start of the season.
"Our run of form is good with three consecutive wins in all competitions," he told Bordeaux's website. "We were solid, not brilliant, and we have to keep our feet on the ground."
Bellion got his chance on Saturday following Yoan Gouffran's move to Newcastle United in the week and because Cheick Diabate is on Africa Cup of Nations duty with Mali.
Fifth-placed Nice, behind Bordeaux on goal difference, also won 2-0 at lowly Brest thanks to centre-back Nemanja Pejcinovic and an own goal by Brahim Ferradj.
Saint-Etienne are one point adrift in sixth spot after a 2-1 triumph at fourth from bottom Sochaux, midfielder Fabien Lemoine notching the winner with his first goal of the season in the 77th minute.
Stade Rennes slipped to seventh, also on 37 points, after Axel Ngando came off the bench to make his league debut and bag the equaliser in stoppage time to secure a 2-2 draw at neighbours Lorient.
The 19-year-old slipped the ball between goalkeeper Benjamin Lecomte's legs a minute after coming on to the field.
"It's great. I try to give everything even if I play only a few minutes," midfielder Ngando told Canal Plus TV.
"The most important thing is to claim one point. I think it will be important at the end of the season."
Rennes started aggressively and had the first clear-cut chance in the seventh minute as Lecomte parried a powerful effort from Romain Alessandrini who was called up by France for the first time this week.
Yann Jouffre opened the scoring for Lorient in the 30th minute after the Rennes defence failed to clear.
The visitors levelled through Turkish striker Mevlut Erding 11 minutes after the break when he went round the keeper to tap the ball into an empty net.
Both sides pushed hard for a second goal and Lorient thought they had secured victory with 10 minutes to go when Jeremie Aliadiere fired into the top corner from 20 metres.
League debutant Divock Origi headed the equaliser in the 74th minute to rescue a 1-1 draw for 2011 champions Lille at home to second from bottom Troyes.
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