Jacqueline McPhie, 46, took the money while vice president for finance at Altus Intervention between March 2013 and April 2014.
McPhie, of Arbroath, admitted embezzlement at the High Court in Edinburgh.
Sentence was deferred to 31 May for background reports.
The court heard McPhie was paid a salary of more than £145,000 a year by the firm, which supplies equipment for North Sea projects.
However, she hatched a plan to divert money from the business to fund her lifestyle.
Alison Di Rollo, prosecuting, said McPhie bought an £80,000 Range Rover, and spent more than £60,000 on a new garage and driveway, £52,000 on a kitchen and £30,000 on a summer house in her garden.
More was spent on foreign holidays and designer clothes.
Ms Di Rollo told the court that McPhie had full "oversight" over the company's finances and had the trust of her employers.
The court heard that Altus had managed to recover more than £238,000 from McPhie.
Judge Lady Wise said: "You have pleaded guilty to extremely serious offences."
McPhie had previously been given 300 hours of community service 16 years ago for stealing £250,000 from previous employers.
She currently lives with her parents in a caravan in Arbroath.
An Aberdeen oil industry executive with a previous conviction for embezzlement stole more than £1.3m from her employers, a court has heard.