The Marcos 1500 GT was launched in 1966, mainly due to diminishing sales and production costs of the 1800, - the whole manufacturing process was streamlined. The introduction of Ford's 1500 GT engine fitted in perfectly with this new model. With 85bhp in standard form, and less weight than the 1800, this became a popular model. Under 100 cars were produced at Greenland Mills between 1966 and 1967.

Construction of the wooden chassis was simplified to cut the cost of production and reduce build time. One of the main changes to the chassis being elliptical torsion boxes as opposed to the triangular type of the 1800. The front sub frame was again simplified by using 1 1/2" square tubing as opposed to the 1/2" diameter round tube of the 1800. The Independent Rear Suspension was dropped in favour of live axle. 

The 1500 was externally identical to the last of the 1800's. Early cars had a bonded in windscreen which was later changed to rubber gasket type. At this time the traditional suspended headlining was also dropped and a foam backed fabric lining was bonded directly to the inside of the roof panel. The body style stayed the same right throughout this model. 

The early cars had the classic French polished walnut veneer dashboard, as opposed to the 1800 with its space age facia. this more conventional flat dashboard still proved too costly to manufacture. After a short period, it was discontinued and replaced by a similar but mass produced wood effect dash. 

The Marcos 1650 followed the 1500 in 1967 being unveiled at the 1967 Racing Car Show. The engine for these cars was developed by Chris Laurence prior to the introduction of the 1600 engine by Ford. The 1650 was a bored out 1500 cross flow engine, balanced with a different camshaft, twin Stromberg carburettors and other modifications. The engine developed 120bhp as opposed to the 85bhp of the standard Marcos 1500. The 1650 engine proved to be a little fragile but filled the gap before the advent of the 1600 crossflow engine from Ford. Approx. 30 Marcos 1500's were made in 1967 at Greenland Mills in Bradford on Avon.