It runs until January 2006 and BCA will handle the sale of about 36,000 vehicles during that time.
The majority of the vehicles will be sold through open auctions at four BCA locations serving the North (Brighouse), Midlands (Nottingham and Measham) and the South (Blackbushe), where BCA will offer the full range of pre-sale preparation through its Smart Prepared division.
There will also be a programme of closed sales for BMW authorised dealers.
BCA says it will deliver a fully integrated nationwide sales and marketing campaign, with a wide range of advertising media supporting the sales programme, along with direct mail, email marketing, online promotions via the BCA website and SMS messaging.
Julie Parmenter, used car manager for BMW Great Britain, said: 'BCA has tailored a physical auction service to handle our different product profiles. It already has a long and successful track record with our companies and we are looking forward to even greater success with this exclusive contract.'
BCA's sales manager, manufacturer sales, Alan Gupwell, added: 'We are obviously delighted to secure this prestigious contract with BMW and Alphabet. We are confident that our market-leading range of services will deliver real benefits to BMW and Alphabet, while offering our buyer base another unique opportunity to purchase quality direct-entered stock.'