Sharon Monelli began quickly from box two to grab the lead, followed closely by kennelmates Luba Monelli and Sveta Monelli, as the trio put an early break on the rest of field.
The order at the top did not change throughout the race and Sharon Monelli rolled on to score by more than three lengths in the race-record time of 27.36sec.
Sharon Monelli also collected the Sandi’s Me Mum Memorial trophy in April and has now saluted in 13 of 43 starts for more than $54,000 in stakes.
It was the third time that Hobby has won the Mandurah Oaks following victories with Groovy Model in 2001 and Disturbia in 2009.
In other racing, Uno Reltub recorded back-to-back wins after a lengthy injury-enforced spell when he took out the Bring Your Team Mixed Stake 1/2 (405m).
Uno Reltub had been on the sidelines since October, but made a winning return to the track a fortnight ago and continued that form when he saluted comfortably by five lengths in 22.46sec.