One of the quads was a demonstration vehicle on display at the Datatool stand at Harrogate Showground. The other was part of agricultural machinery suppliers Carrs Billington's stand.
Datatool specialises in providing electronic tracking and security devices for motorcycles and farm ATVs, and boasts a 96 per cent theft recovery rate.
They are official security suppliers to brands including Honda and Yamaha.
Quads and other ATVs have proved popular among thieves who target isolated farms and rural properties in recent years.
North Yorkshire Police said: "The incident happened at the showground between 3-4am on Wednesday 13 July when the quad bikes were taken and believed to have left in the direction of Wetherby Road.
"We are requesting the public's assistance to help establish the full circumstances surrounding the incident.
"In particular, we are appealing for anyone who has information or who witnessed anything suspicious around the area at the time of the theft.
"Anyone with information that could assist the investigation should email: [email protected] or call 101, select option 2, and ask for PC 1606 KINNEAR
"If you'd prefer to remain anonymous you can call Crimestoppers on 08000 555 111
"Please quote ref: 12220121553."
A spokesman for Datatool said: "On the morning of Wednesday 13 July at 03:29:55, our monitoring centre was alerted of movement on the two ATVs, one of which was lent to Datatool for display and had been fitted with a Datatool Stealth stolen vehicle tracker.
"Our 24/7 monitoring team tried contacting the owner of the ATVs but was not successful in reaching them, resulting in six missed calls and theft notification alerts.
"As there was no confirmation of theft from the owner, police forces won’t accept direct communication from any telematics company after a potential theft situation is alerted. The tracker had subsequently been removed by the criminals 15 minutes after the initial theft notification and they were then able to escape with the quad bikes, undetected by the Showground security.
"Priding ourselves on our 96 per cent theft recovery rate, we do however see a small number bypass our means of recovery and unfortunately, this was one of those occasions. This anomaly is disappointing for everyone at Datatool, especially our in-house monitoring team who have worked tirelessly to help recover close to £17,000,000 worth of vehicles this year alone."