Grenland Group was established on 27 September 2004, as a result of the merger between Grenland Offshore Holding, Karmøy Stålindustrier and Hitec Framnæs. However, its origin was Grenland Offshore, founded in 1991 and acquired by Hallgeir Skogen in 1993. 

2012
Grenland Group AS acquired 51% of the shares in the company Erbus AS on 4 January.
Grenland MMO AS was merged into Grenland Industri AS on 1 January. Grenland Industri AS changed name to GG Operations AS.

2011
Grenland Group Electro & Automation AS is merged into Grenland Industri AS on 1 September.
Grenland KSI AS located at Skudeneshavn (Karmøy) was closed down in August.
Grenland Group acquired 49% of the shares in Athene Solutions AS in Stavanger in July.
Grenland Group ASA was delisted from Oslo Børs on 20 May.

2010
Otto Søberg was appointed CEO of Grenland Group on 10 December.
Hallgeir Skogen resigned as CEO & President of Grenland Group on 5 November, and sold all his shares in HVS Invest AS to HitecVision AS.
Grenland AsIs Global AS in Stavanger was sold.
Opening of Bergen office by acquisition of CIC Engineering.
Opening of 'Grenland House' in Sandefjord, a brand new, state-of-the-art office building.

2009
Hallgeir Skogen took over as CEO & President of Grenland Group
Grenland Arctic AS in Harstad was sold.

2008
Terje Uthus was appointed CEO & President of Grenland Group.

2007
Opening of Grenland Group’s Asia headquarters in Shanghai, China.
Acquisition of Elteka Teknikk in Skien, Norway (that became part of GG Electro & Automation).

2006
Acquisition of Nopicon and Real Concept Group (now part of Grenland Group Technology).
Establishment of Grenland Arctic in Harstad, Norway and Grenland Group Electro & Automation in Stathelle, Norway
Acquisition of Minox Technology (now part of Grenland Group Technology).

2005
On 12 December, the company was listed on Oslo Stock Exchange.
Establishment of Grenland Advanced Engineering in Houston, USA and Grenland Nusantara in Kuala Lumpur, Malaysia.
Acquisition of the operating company of Heerema Norway in Tønsberg. 

2004
Acquisition of Bjørge Offshore, that became part of Grenland MMO.
Grenland Group was established by the merger of Grenland Offshore Holding, which consisted of Grenland Offshore, Grenland Industri and Grenland Maskinering, and the Hitec Industrier companies; Karmøy Stål Industri (later named Grenland KSI) and Hitec Framnæs (now Grenland Group Technology).

2000
Grenland Offshore acquired Brødrene Sørensen that changed name to Grenland Industri.

1997
Hitec Framnæs was established after changing its name from Framnæs Engineering. Hitec Framnæs’ roots go back to 1973. (Now Grenland Group Technology).

1974
Horten Verft took over activities at Langesund yard. The company returned to shipbuilding with production concentrated on the centre sections of large tankers.

1967
The firm Sverre Munch AS, based in Bergen, Norway, acquired the company, and the production and mounting of ship cranes began.

1948
Langesund Shipyard built the first of a series of ''lake ships'' that the shipyards gradually became famous for. The lake ships were specially constructed to fit through the locks leading into North America's Great Lakes.

1940
The German attack on Norway 9th April 1940 came as a total surprise to the average Norwegian. Soon after the invasion, Langesund Shipyard was also taken over. During World War II, the shipyard was under German control and produced barges and obstruction buoys, and a few merchant ships, amongst other things.During the early stages of the World War II, the shipyard delivered the cargo steamer ''Sallaä'' for a Finnish shipping company.

1930
Times were not good for the engineering industry during the great depression period. But in the last half of the decade, life gradually got better. However, the depression affected the different industrialized countries (including Norway) in various ways and degrees of intensity.Even during this period, the production at the yard never stopped. The main production was related to repairs and maintenance of laid-up vessels. The shipyard also delivered the cargo steamers, ''Havmøy'', ''Vigør'' and ''Tunisia'' during this decade.

1920
The Langesund Shipyard experienced difficult years. Scarcity of work forced corporations to lay off or dismiss many of their employees. It was a period with many strikes and lockouts, which also took place in Langesund. Even so, the shipyard continued to deliver vessels. Among vessels produced during this period are the cargo steamers, ''Lionell'', ''Innaren'' and ''Torridal''.

1880
Langesund Shipyard, the industrial revolution: The period between 1880 and 1920 became the great era of mechanical workshops in Norway. The shipyard mostly repaired sailing vessels and built small iron barges. The shipyard's first delivery was the cargo steamer ''Terneskjær'' in 1918. The following year, the cargo steamer ''Eikhaug'' was delivered.

1712
The frigate "Løvendahl's Galley" was built for the great Admiral Tordenskiold. The ship was a 90-foot frigate, armed with 18 cannons. The small frigate sailed during the Great Northern War (1700-1721), under the command of Peter Wessel "Tordenskiold'', the outstanding naval hero of this war.