Magherafelt R.F.C. was founded in 1928. Some success at minor level came the club's way before the outbreak of war. A few games were played during the war years and from 1947, the club became known as Rainey Old Boys R.F.C. After initial success, a barren period followed and it was not until the mid-60s that the club began to go places.

Rainey Endowed School, coached by Dawson McConkey, became a power in Ulster and when Dawson joined the Old Boys as player/coach, they rose to the top of the junior ranks with a very talented young side. By the mid-70s, Rainey were the leading side in junior rugby in Ulster, winning most of the major trophies.

In 1982 the club went on tour to the Bahamas and the following year won the Town's Cup for the first time. On that team were twelve times capped Harry Steele and brother-in-law, Alan McLean, an Ulster regular who toured Australia with Ireland in 1979.

The President from 1984-1990 was Dr. A.A. McConnell (Bertie), who was a member of Ireland's Grand Slam side in 1948.

Rainey proved to be a good cup side but were relegated to Section 2 in 1986. They won Section 2 the following year but slipped back down again in 1994 despite reaching the Town's Cup final for the sixth time in twenty years. With former Ulster lock Charlie Simpson as player/coach, they won the Town's Cup in 2001 and were promoted as champions the following season.

Former Ballymena No. 8, John Andrews, took over as player/coach when Charlie moved on to Dungannon, and led the side to the Qualifying League 1 title in 2005. In the play-offs they beat Monivea 21-8 at home before losing 14-13 at Naas and 18-17 at Nenagh Ormond.

Having added some strength in depth to the squad, they started the next season by beating Ballymena 2s in the Past Players' Cup Final. After twelve straight wins in the league, they came unstuck at Armagh on New Year's Eve but regrouped to beat second placed Limavady 53-3 and retain the title. In the inaugural All-Ireland Junior Cup the luck of the draw helped them to beat Cork side Kanturk 47-9 and South Dublin outfit, Seapoint 31-12 at home. A big crowd travelled south to see them beat Youghal 27-5 at Lansdowne Road in the final on April 8th. Then on successive Saturdays, they beat Westport 36-0 away, Youghal 34-0 and Monkstown 32-16 at home to win the round robin play-offs and clinch their place in the All-Ireland League.

In 2008/09, With South African Rhys Botha as Player/Coach and Andrew Kerr as Captain, Rainey turned in some very promising performances in the Ulster League, beating Ballymena once again at Eaton Park.  A fine victory over Instonians at Shaw's Bridge earned them a home tie against U.C.D. in the second round.

They opened their AIL campaign with a win at Banbridge, but their aspirations of a top four finish disappeared when player after player joined the injured list, including Willem Jacobs, an overseas recruit from South Africa.  While their home form was strangely poor, they produced some battling displays at Suttonians, Ards and Sunday's Well to finish in 10th place.

Richard McCrea was captain for season 2009-2010.  Forty-seven players were used as player after player went down injured.  Limerick side Old Crescent were visitors in the Cup before the AIL got under way.  New Zealander Tony Dodunski picked up an injury within five minutes of his debut and was out for six weeks.  Hopes of a top half finish turned to survival and a narrow victory at Portadown proved vital.  An unexpected draw at Midleton, who were promoted behind an outstanding Queen's team, was a timely boost and late season home wins over Instonians and Ards took Rainey up to the thirty point mark and again tenth spot in the table.

Season 2010-2011, with Rodney Paul as captain, was a truly remarkable one.  A chronic injury list saw the side struggle in the Ulster League and lose the first four games in Division 3 of the AIL campaign, but the return to fitness of New Zealand scrum-half Peter Sciascia and a host of others kick-started an outstanding run, spoiled only by an intercept try against Nenagh.  A record total of 46 points hoisted Rainey up to sixth place.

This run of success continued when Simon Hawe took over as captain.  After a great start, a little mid-season sticky patch was to severely dent promotion prospects, but a fine finish earned the club fifth place on 48 points in Div 2B of a restructured AIL.  The ability and character of the squad was evident when all-conquering Cashel were extremely fortunate to beat them 20-17 at Spafield on the final day of the campaign.  Neil O'Kane was chosen as Player of the Year for the fifth time, while the very popular Peter Sciascia returned home, having given the club many moments to remember.