In what turned out to be its only season in the senior ranks, the club reached the grand final, played at the Brisbane Cricket Ground on 4 October, but fell to a 3-1 defeat against Pineapple Rovers.

[11] Two weeks later Merthyr Thistle rounded off the season on 18 October in the final game of its existence, a challenge match at Bulimba against Bush Rats, one of the leading clubs in the Ipswich competition, losing 1–0.

So convivial was the atmosphere that the Ipswich Times report stated that “when the players were ready to return to the city they lined up and the Pipers’ Band led the way to the ferry.

In a 5-2 victory at Heath Park, W Nicholls had the honour of scoring the club's first goal, with Jock Cumberford and Bob Craig each netting a brace.

[17] A few days later, the Queensland British Football Association placed its 30 registered junior clubs into three grades for the forthcoming season.

[19] On the official opening day of the 1920 season, 10 April, Thistle played the club's first competitive match, defeating Queen's Park 3–1 at the Brisbane Cricket Ground, with the following lineup: H May, W McBride, G Mackay, D Ross, J Peebles, J Lambert, J Cumberford, A McMillan, R Craig, A Thompson, W Nicholls.

[20] The highly successful first season ended with 10 wins, two draws and three defeats to place Thistle in second position behind Corinthians on the premiership table.

Thistle's tenure at Heath Park was confirmed the following season when an application for use of the ground was approved by the Brisbane City Council, at an annual rent of one guinea.

But Thistle made no mistake just one season later, annexing their first major honour by claiming the 1923 Brisbane premiership with a 5–1 win in the Challenge Cup replay against Bundamba Rangers.

Jack Cumberford, who coached the Queensland team after World War II, earned a unique honour when he was awarded a special medal for scoring Australia's first international goal in a 3–1 win against Wanganui in the opening game of the tour of New Zealand in 1922.

However, the following season saw one of the code's periodic upheavals in Queensland when Brisbane's leading clubs, with the sole exception of Thistle, decided to break away from the state governing body and form a company to run their affairs.

[30] By the end of the 1931 season, however, the club was struggling on and off the field, having finished last in the 10-team Ipswich competition and facing severe challenges during a period of world-wide recession.

In March, 1932 the Sports Referee reported that although members at the Thistle annual general meeting were determined to continue, the club was in deep financial difficulty, with a credit balance of £1/5 and liabilities of £4/10.

Poor attendances at Lanham Park meant that only £8/16/4 had been collected during the entire preceding season and travel expenses for regular trips to Ipswich had also depleted the club's resources.

There was no change to playing personnel, home ground, club officials or top division status, except that long-serving Thistle stalwart Bob Jardine was elected as incoming president for the season ahead.

[2] For the second time in the club's history it was facing relegation after finishing bottom of the table in that season, but once again a split in Queensland football came to the rescue.

Formation of the breakaway Queensland Soccer Federation at the start of the 1962 season enabled Thistle to join other leading Brisbane and Ipswich clubs in an eight-team semi-professional competition in which a respectable mid-table position was secured.

This was largely due to the influence of diminutive Scottish captain-coach Norm Tran, whose acquisition from East Fife provided the impetus for a club revival.

This time the catalyst was the signing of Jim Hermiston, a member of the Aberdeen team which beat Celtic 3–1 to win the Scottish Cup in 1970.

In 2021, the club defeated Caboolture 3-1 in the grand final of the inaugural season of Football Queensland's Premier League 2 competition, having finished third on the premiership table.