The club was formed at a meeting held on 17 October 1876 under the presidency of the Reverend Marriner. A committee was elected and the club was allowed the use of Holmes' field in Lawkholme Lane.
The first kick-off took place on Saturday afternoon, 21 October and the committee met again on 24 October and decided to adopt Association and Rugby football laws. On 18 November 1876, the first game took place at Lawkholme Lane. The visitors were Crosshills and although the game ended in a draw, there are records, which say, "the draw was in the visitors' favour".
The first important match appears to have been played on 13 January 1877 against Bingley. Under the scoring system of the day, the visitors won by two tries and two touchdowns to two touchdowns. Keighley also lost a further two games against Bingley.
One of the earliest games of the following season was a fixture with Kildwick on 13 October 1877 when Keighley won by one goal to five touchdowns. Other teams met during that second season were Bradford Zingari, Manningham, Cleckheaton, Leeds Athletic, Skipton and Bradford Juniors. Up to April 1878, Keighley and Bingley had met seven times with Keighley losing every match.
At the annual meeting of the club in 1878, shortly after the headquarters had been moved to Dalton Lane, a second XV was formed. Keighley Athletic were formed on 27 October 1879. There was some rivalry with those who had set up the new club, but a couple of years later these differences had been settled, and on 24 March 1881 a merger was agreed between the two clubs.
Keighley officially joined the Rugby Football Union on Tuesday, 8 April 1879, and the following year, in a match at Bingley, there was a peculiar incident. A report of the game states that Bradbury attempted a drop goal, but the ball passed under the crossbar, and Bairstow, following up, touched down. Bingley would not concede the try, alleging that the player who obtained it was offside, and due to their refusal to allow the ball to be brought out, the home players left the field and the game was unfinished.
By the end of season 1880–81, the membership of the club was 80; ten honorary members and 70 playing members. In 1882–83 "the team had a most successful experience". Gate receipts reached £58 and expenditure was £32.
In March 1882, the team figured in the Yorkshire Cup for the first time. They met Wakefield Trinity, who were one of the top sides. During that year, a match with Hunslet F.C. was played under Association rules which ended in a draw. It was probably the only Association game ever played by the town's club.
In April 1885, the club merged with Keighley Cricket and Football Club, and from that time the club played on the Lawkholme Lane ground. Soon membership had risen to 300 and dressing rooms and headquarters were established at the Black Horse Hotel. The first game at Lawkholme took place on 10 October 1885, against Liversedge. The club's fixture list was improved and in 1886–87 played clubs such as Hipperholme and Lightcliffe, Bramley, Otley, York, Shipley, Ossett, Bingley, Pudsey, Halifax Free Wanderers, Morley, Skipton and Hunslet.
The club reached one of its best seasons in 1892–93 when the team figured in several rounds of the cup and won no less than 22 matches during the season. Leagues were being formed about this time and in 1893–94 Keighley had a try at the Intermediate Competition and finished sixth with a record of eleven wins and eleven defeats.
The following season the club did badly and finished tenth, but in 1895–96, the side came into its own again and finished fourth.
The sweet taste of success came Keighley's way in 1896–97 when they won the Second Competition championship. The final match of the competition took place at Mytholmroyd on 3 April 1897, and despite a bitterly cold day there was a gate of 2,000 of which over half had travelled from Keighley. Keighley won 6–3. This heralded a run of success which saw them win the First Competition championship in 1899–1900 after having been runners-up the two preceding years.
By early 1990s things had become almost critical for Keighley, as the ground was decrepit and the team was losing to the likes of the now defunct Nottingham City.
That’s when, in 1991, Mick O'Neil, Mike Smith and Neil Spencer joined the board and embarked on re-branding; the first being adding Cougars to their name. O'Neil became Chairman of the club and started the trend for iconic music for each player after they scored, lively PA announcements and active on-field mascots. Mary Calvert, a community relations adviser, was also appointed. Bringing a new perspective, Mary encouraged the involvement of local school children, opening the "Cougar Classroom" and launching initiatives such as drugs education.
At director level, Mike Smith was in charge of the positive marketing and the like; Neil Spencer was in charge of finance and the youth academy. All of which made visits to Cougar Park in the mid-1990s a progressive and eye-opening experience for rugby league supporters. The club attracted the attention of the national press and senior politicians, which remains unique in rugby league. The club was feted by then Prime Minister John Major for its massive success, huge attendance increases, unique community involvement and investment in top flight players and facilities.
Peter Roe returned to the club as head coach in September 1991 and stayed until 1994.
In 1993, the Cougars won the third division only to be denied promotion due to the Rugby Football League merging the second and third divisions.
Investment in good players, and an expansive style helped crowds increase from 350 in 1989 to an average of over 4,000 in 1995, and on-field success followed. The club invested heavily: in new terracing; a new club-house; the Great Britain coach Phil Larder; and a full-time Premier League standard team.