The Buick Rainier was first introduced in 2004 and was manufactured until its discontinuation with the 2007 model year. It was the first SUV with the Buick emblem, but shared the same truck based platform as the Chevrolet Trailblazer, GMC Envoy and Oldsmobile Bravada 5 passenger midsize SUVs. Although the Rainier was intended to be the luxury model amongst its brethren with a slightly different exterior style and a few more comfort features, it received only minor changes throughout its lifetime and the continual use of sub par materials, sloppy handling and restrictive design prevented the Rainier from becoming much more than a big mistake.

On a positive note, the Rainier was continually equipped with the same strong powertrain from 2004 until 2007. Initially offered in a CXL and CXL Plus trim, both models came standard with a 4.2 inline 6 cylinder that delivered 275 horsepower mated to a 4 speed automatic transmission. A more powerful V8 engine was optional, producing 290 horsepower, and both engines accelerated well. Both models were also available with either rear wheel drive or all wheel drive, though the all wheel drive system did not have a low range which made the increased traction better suited for wet or snow covered paved roads than off road excursions. One of the most impressive features of the Rainier was its 6700 pound tow rating. Another worthwhile standard feature that really worked was something that was termed 'Quiet Tuning', which was basically the inclusion of sound deadening materials that were positioned around the engine, doors and quarter panels to decrease road noise inside the cabin. Enhancing this concept was the addition of an acoustic laminate material over the windshield and front side windows.

The CXL Plus trim was removed from the lineup in 2005, leaving behind the CXL as the lone model. Standard features included 17 inch wheels, power operated leather seats and dual zone automatic climate control. Additional features could be purchased separately as stand alone options or option packages that grouped some of the more popular creature comforts. For the 2006 model year, the inline 6 cylinder was modified to increase horsepower to 291 and a much needed stability control system was added as part of the standard equipment package. The 2007 model saw the addition of the OnStar navigation system.

The Buick Rainier entered the SUV market at the right time and consistently offered more than adequate powertrains and a quiet ride, but its lack of refinement, features and its unreliable handling eventually contributed to its demise as more flexibly designed and full featured vehicles took the lion's share of SUV sales. The Rainer was replaced for the 2008 model year by the Buick Enclave.