The company traces its roots back to the late 1800’s when George Quinion partnered with Leavitt Trucking (founded in 1877) to form the Leavitt & Quinion Trucking Company. A few years later, George assumed control of the business, added coal sales and changed its name to The Quinion Coal & Trucking Company. The evolving business operated from a storefront on North Main Street in Bristol and became a recognized name in the area. When oil and kerosene fired heating equipment began to appear in the 1920s, George instantly recognized their potential. He transitioned the business to the delivery of fuel oil and kerosene and added a service department that specialized in the installation and repair of the then “state of the art” Timkin burned, furnaces and boilers. Hence, George prepared the business to take advantage of the boom in equipment conversions and new construction of the 1940s and the 1950s.

Business flourished and George arranged the construction of a new office and the bulk plant in 1963 on Terryville Avenue in Bristol, which still serves as the company's current headquarters. With his love for the business and no children interested in joining him, George continued to operate his business past retirement age. 

In 1976, George’s grandson Brett Quinion and Brett’s close friend Don Phillips began working full-time in the business upon high school graduation. Brett gravitated to the oil delivery side of the business, while Don pursued training on the service side. In 1979, George Quinion, still active in the business, passed away at the age of 90 and control of the business passed to Brett. Over time, Brett demonstrated a zeal for growing the top line. He immediately changed the name to Quinoco (short for the Quinion Oil Company) and acquired multiple competitors throughout the 1980s and 1990s: Kellert Oil (Burlington, CT), Norton Oil (Bristol, CT), Breen Oil (Bristol, CT), Vics Oil (Terryville, CT), Santoro Oil (Torrington, CT), A&W Oil (Torrington, CT), and Sholtis Oil (Torrington, CT).  

The business thrived and the company's service area expanded into Farmington Valley and much of Litchfield County. The acquisition of A&W Oil in Torrington added an office on Migeon Avenue in Torrington and a distillates bulk plant on North Elm Street. At this point, Don Phillips became manager in the service department and focused on increasing system installation sales, while adding cooling equipment and ductwork fabrication to the company's capabilities. Don championed the company's emphasis on quality by offering equipment from only high-end manufacturers such as Thermo Pride, Buderus, and Riello. 

In 2002, Brett Quinion decided to pursue his dream of coaching high school football and sold the company to Don. Don continued to grow the business, but recognized the need to diversify and began selling propane in 2009. In late 2009, the company acquired Cadwell Oil (Farmington, CT), which strengthened its Farmington Valley presence with a physical location. To support the company’s growing propane business and secure product supply, the company constructed a 60,000 gallon propane bulk plant at its Farmington terminal in 2012 and a second one in 2018 on an acquired parcel in Torrington. The company’s long standing presence, commitment to higher-end service, and flexibility continues to make the company an energy provider of choice within its market.