Like Oldsmobile's F-85, Buick's Special graduated from senior compact to a mid-sized model in 1964 thanks to the introduction of GM's new A-body platform, a full-frame foundation that rolled on a 115-inch wheelbase. As before, the next-generation Skylark was adorned with special trim and an upscale interior. Bucket seats were standard for the topless A-body Skylark, but optional for its hardtop running mate. A four-door Skylark sedan also entered the mix in 1964. A cast-iron V-6 displacing 225 cubic inches was standard that year, with a 300-cid V-8 available as an option. A two-door sedan joined the mix in 1965, and both the V-6 and V-8 Skylarks were available through 1967.

In 1965, Buick used the Skylark as a base for its GTO knock-off, the Gran Sport. Offered as a coupe, hardtop or convertible, the '65 GS was powered by the full-sized Wildcat's 325-hp 401-cid V-8. In 1967, the Gran Sport became a stand-alone model as the GS 340 and GS 400.