Slaven Bilic’s team saw both their nearest rivals win on Saturday but showed few hints of nerves a day later as they brushed aside Trabzonspor 3-0.
Veli Kavlak gave Besiktas an early lead that was doubled by Demba Ba midway through the first half.
Four minutes from time, Cenk Tosun made sure of the points - Besiktas have 26 at the summit, one ahead of Galatasaray and two better off than the defending champions.
Raul Meireles struck five minutes before half-time, allowing Fenerbahce to close out a hard-earned 1-0 victory at Balikesirspor.
A goal in each half from forward Burak Yilmaz helped Galatasaray to a 2-1 victory against Akhisar Belediyespor, for whom veteran Greece international Theofanis Gekas' late effort was not enough.
Fifth-place Bursaspor were the weekend's big winners as Fernandao bagged a brace in the 5-1 thumping of Kasimpasa.
The Brazilian got the ball rolling in the third minute and completed his double after Josue netted from the penalty spot.
Ozan Tufan and Volkan Sen got in on the act, meaning Ryan Babel's 86th-minute goal stood as the faintest of consolations.
Karabukspor were similarly impressive, dispatching fellow strugglers Rizespor 3-0 to move out of the bottom three.
Onur Ayik scored a 17th-minute opener and Joseph Akpala starred with goals in the closing stages of each half.
Istanbul Basaksehir saw off Eskisehirspor 1-0 and they lie sixth thanks to Semih Senturk's goal.
There were 2-0 home wins on Saturday for Konyaspor and Genclerbirligi over Mersin Idmanyurdu and Gaziantepspor respectively.
Sivasspor rounded off the round with a 1-1 draw against Kayseri Erciyesspor on Monday night despite having forward John Utaka sent off.
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