A solo attack about the 25-minute mark on The Esplanade circuit would prove to be a winning move for Mullens.

"It's taken 10 years, but I have finally done it," an ecstatic Mullens said after round three in the Mitchelton-backed series which began with rounds on Geelong's Ritchie Boulevard and Eastern Park.

Many of her previous Bay Criterium campaigns involved placings.

"There have been team classification wins, and the sprinter's title (last year), but I had never won a round," Mullens said.

"As the years go on there have been doubts as to whether I would ever win a Bay Crits race.

"There's only four races  a year and the quality of the field just keeps getting better each year."

After racing to fourth place in Friday's opener, Mullens took a break on Saturday.

"The plan (for Portarlington) was to be aggressive the whole race, be opportunistic, and just have a crack."

Early on it was Mullens and round two winner Gracie Elvin who did plenty of attacking.

Another attack by Mullens in the 25th of the 45-minute duel was to be decisive as she quickly gained a 20-second lead on the pack.

The lead was whittled to six seconds, but Mullens would not be denied victory this time.

The Bendigo ace powered to victory ahead of Italy's Georgia Bronzini, Lauren Kitchen, Lizzie Williams and Chloe Hosking.

Victory pushed Mullens to fourth in the series standings on 19 points behind Hosking, 26; Kitchen, 24; Williams, 20; and Elvin, 17.

Despite her success on the streets, Mullens will not race in Monday's finale at Williamstown.

"The crits series is great, but my main focus is on the road nationals."

The Cycling Australia championships start with Wednesday's criterium in Ballarat.

Mullens was runner-up in last year's race.

Number one priority is Saturday's road race on the Mount Buninyong circuit.

Once the road nationals are done, Mullens will be back on the mountain bike to prepare for round two in the national series.

She began the 2014-15 campaign by finishing second in the cross-country race at the You Yangs.

Mullens was 12th in the MTB cross-country final at last year's Glasgow Commonwealth Games.

On the road, Mullens is sponsored by Seight Custom Clothing and Sram.

Backers for the MTB campaign are Sram and Yeti.

The  multi-talented cyclist is a monthly winner in the Bendigo Bank Bendigo Advertiser Sports Star of the Year award.

Now in its 50th year, Sports Star is proudly supported by Prime 7. The awards golden anniversary will be celebrated on February 27.

Meanwhile, NSW young gun Caleb Ewan has stitched up a second Bay Criterium series.

The 20-year-old again streeted rivals in Sunday's race at Portarlington.

Youngest win in Bay Crit history two years ago, Ewan is on the brink of becoming the first cyclist to be unbeaten in a series.

Bendigo's Jack Haig, racing for Avanti, was 14th in Sunday's race.

First of Monday's races at Nelson Street, Williamstown is at 11am.