The Glasgow firm will provide filtration, water treatment and pumping equipment for seven pools plus pipework and controls for flumes, play structures and water features.
It comes after the business won £700,000 of work earlier this year to refurbish the swimming pool and add new features at Center Parcs Elveden Forest.
The £250m Center Parcs complex at Woburn Forest is expected to open in spring 2014 with 625 lodges and a 75-bedroom hotel alongside leisure activities and retail premises.
Staff from Barr + Wray are working on the design of the swimming area and a team of up to 16 engineers are due on site early next year.
Barr + Wray was appointed by the main contractor, Derbyshire-based Bowmer & Kirkland, following a competitive tender.
Alister MacDonald, managing director of Barr + Wray, said: "It is the largest single contract we have won in the UK in recent years.
"Through the work we have done over the years for Center Parcs we have a close relationship with the development team there. We did bid for it competitively and thankfully we were successful.
"We won't be starting on site until early next year and the size of the team on the ground at any given time will just depend on the workflow."
Don Camilleri, Center Parcs Woburn construction director, said: "The Subtropical Swimming Paradise is an iconic part of Center Parcs in the UK and has been for more than 25 years.
"It was important we selected a provider that we trusted to keep the water flowing every day of the year and did so while minimising energy usage."
Barr + Wray, which employs 100 people across the UK, was involved in building seven temporary swimming pools for the London Olympics.
It is now decommissioning those, with only two remaining to be dismantled before the end of this year. Further to that it installed a spa for athletes at Commonwealth Games venue the Emirates Arena in Glasgow.
Mr MacDonald indicated that the company – which was founded in 1959 as a distributor of pump and filter products – continues to see much of its sales growth from the Middle East, where it employs 17 people in Dubai, and Asia which is served by four staff members who are based in Hong Kong.
It has exported to more than 40 countries, with clients including global hotel groups such as Mandarin Oriental, Four Season and Jumeriah.
Mr MacDonald added: "We haven't published our accounts yet for the year to end of September but it will be another year of growth in turnover and profitability.
"We have managed to have a relatively stable business in the UK but the growth is mainly from what we are doing overseas."
Barr + Wray Group reported an increase in turnover from almost £15m to more than £17m with pre-tax profits up from £929,873 to £1.15m in the 12 months to September 30, 2011.