Born in Brisbane, Queensland, the son of former Queensland cricket captain and opening batsman Sam Trimble, Glenn Trimble attended Brisbane State High School and played in the cricket team.

Trimble was selected for the Australian Under 19 team in February 1982 and played three "tests" against the touring Pakistan U-19 team. (The captain was Mike Veletta and his teammates included Craig McDermott; Saleem Malik captained the Pakistan side). He scored 116 in the second test. He scored 232 runs over the 3 tests at 46.

1982-83: Queensland debut

Trimble made his Queensland debut in 1982-83 against WA, scoring 48.

1983–84

The following summer he made 84 in a Shield game against Victoria and scored useful runs in a Queensland one day victory over the touring West Indians.

Other highlights that summer included 99 against Victoria and 71 against Tasmania. He played in the Shield final, which Queensland lost to WA; Trimble scored 0 and 6.

1984-85

Trimble impressed over the 1984-85 summer with 42 for Qld against the touring West Indies., 90 against Victoria. and 67 not out against South Australia.

He made a century against Sri Lanka in a one day game. but then suffered a form slump.

His form recovered towards the end of the summer making 76 against South Australia. He scored some useful knocks of 38 and 16 in the Sheffield Shield final, which Queensland narrowly lost to NSW.

1985–86 season: All rounder

Trimble began the next summer well with 90 against Victoria. In a game against the touring New Zealand side, Trimble made 49 and 26. He had only bowled one first class over before but was given the ball and took 2-0 in his first over, and four for the game

Trimble took 2-63 against South Australia, scored 41 and took a wicket against WA, then took five wickets against Tasmania. After scoring 75 and 41 and taking two wickets against Victoria Trimble was picked in the Prime Ministers XI to play New Zealand.

He made 87 and took five wickets against South Australia.

One Day Internationals

In January 1986 Trimble was selected in the Australian one day team as a replacement for David Hookes against the touring New Zealand cricket team.

"I was elated, I really didn't expect it and laughed off a suggestion I was even close," Trimble said. "But Dad rang from his sports centre at the Gabba and then raced in with a grin all over his face — it was all over mine too. I suppose I can now start to think that some success and more hard work could get me to New Zealand in February or India later in the year."

Trimble made his ODI debut at Perth's WACA Ground to bolster the batting, replacing David Gilbert. He dropped a catch in the gully. He was given the ball when New Zealand was 4-61. His first delivery was a bean ball which Jeff Crowe fended off for 2 runs, the second, another full toss, was dropped by keeper Wayne Phillips and was ruled a no ball. The third ball was a full toss which was hit for four. He bowled an erratic spell, having two chances dropped off his bowling. He was taken off after conceding 32 runs off four overs. He then batted at number eight and was not out zero facing three balls. Australia won the match by three wickets.

According to one report, "Trimble had a rough entry to international level before nearly 25,000 Perth fans and millions of TV viewers around Australia who wanted to see him fire. However, he was chosen on more than one good performance and won't be dumped completely after a single poor effort."