O'Reilly was one of the best spin bowlers ever to play cricket. He delivered the ball from a two-fingered grip at close to medium pace with great accuracy, and could produce leg breaks, googlies, and top spinners, with no discernible change in his action.
A tall man for his day (around 188 cm, 6 ft 2 in), he whirled his arms to an unusual extent and had a low point of delivery that meant it was very difficult for the batsman to read the flight of the ball out of his hand. According to Matthew Engel writing in Thirty Obituaries from Wisden, "When O'Reilly died, Sir Donald Bradman said he was the greatest bowler he had ever faced or watched. In 1935, Wisden wrote of him: "O'Reilly was one of the best examples in modern cricket of what could be described as a 'hostile' bowler. In 1939, Wisden reflected on Bill O'Reilly's successful 1938 Ashes tour of England: "He is emphatically one of the greatest bowlers of all time."
As a batsman, O'Reilly was a competent left-hander, usually batting well down the order. O'Reilly's citation as a Wisden Cricketer of the Year in 1935 said: "He had no pretensions to grace of style or any particular merit, but he could hit tremendously hard and was always a menace to tired bowlers."
As well as his skill, O'Reilly was also known for his competitiveness, and bowled with the aggression of a paceman. In a short biographical essay on O'Reilly for the Barclays World of Cricket book, his contemporary, the England cricketer Ian Peebles, wrote: "any scoring-stroke was greeted by a testy demand for the immediate return of the ball rather than a congratulatory word. Full well did he deserve his sobriquet of 'Tiger'.
When he was three, the O'Reilly family moved to Murringo, which O'Reilly said in his autobiography Tiger, played no vital part in his cricket education. However, in 1917, at the age of twelve, the family moved 30 kilometres north to the town of Wingello. Wingello was a cricket town and "everyone was a cricket crank" according to O'Reilly. It was here that he developed a passion for the game. In the early 1920s, O'Reilly's brother Jack moved to Sydney. One afternoon, Jack watched spin bowler Arthur Mailey in the North Sydney practice nets and managed to describe the famous bowler's 'Bosie' action in a letter to Bill. O'Reilly claims to have perfected the action of changing the spin from anticlockwise to clockwise without any discernible hand movement within a couple of days. "The bosie became my most prized possession. I practised day in, day out", he said.
He played representative cricket as a schoolboy, including matches against Don Bradman's Bowral team, a match which O'Reilly himself later described thus:
How was I to know that I was about to cross swords with the greatest cricketer that ever set foot on a cricket field ? ... by the close of play, 17-year-old Don Bradman was 234 not out. The match resumed a week later, according to the local custom ... I bowled him first ball with a leg-break which came from the leg stump to hit the off bail. Suddenly cricket was the best game in the whole wide world.
He went to St Patrick's College, Goulburn as a boarder in 1921 and quickly showed his athletic flair by becoming a member of the school's football, tennis, athletics and cricket teams. He held a state record for the hop, step and jump. O'Reilly later won a scholarship to the Sydney Teachers College at Sydney University, where he played in a David Jones Second XI and against journalist Johnny Moyes, who wrote about O'Reilly's skills glowingly.
O'Reilly became a regular member of the Australian Test side in the 1932–33 season and he played in all five Tests against England in the famous Bodyline series. He was the team's leading wicket-taker with 27 wickets, and his 10 wickets in the second match of the series, at Melbourne, where he opened the bowling, enabled Australia to square the series after England had won the first match. The controversial "leg theory" bowling used by England under newly appointed captain Douglas Jardine brought the touring team victories in the remaining three matches: Australia were handicapped not only by the tactics, but also by a lack of fast bowling, which saw O'Reilly also opening the bowling in both Adelaide and Brisbane, and by a decline in the form of Grimmett. O'Reilly not only took most wickets but he also bowled by some distance the most overs on either side, and he achieved a bowling economy of less than two runs from each of his 383 eight-ball overs.
In the 1933–34 season, with no Test series in Australia, O'Reilly finished top of the Sheffield Shield bowling averages, taking 33 wickets at an average of 18.30. Against Victoria at the MCG, he took nine wickets for 50 runs in the second innings. He was selected for the tour of England in 1934, where he and Grimmett were the bowling stars as Australia regained the Ashes. They began by taking 19 of the 20 England wickets to fall in a comfortable victory in the First Test at Trent Bridge. O'Reilly's match figures were 11 wickets for 129 runs, and taking seven for 54 in his second innings was to produce his best Test figures. England then won the Second Test at Lord's, but O'Reilly shook English confidence in the Third Test, at Old Trafford, by taking three wickets in four balls — Cyril Walters, Bob Wyatt out for a duck, then Walter Hammond second ball after leg-glancing his first for four — but the high-scoring match never looked likely to produce a result. A further draw at Headingley, with England saved by rain after a Bradman triple century, set up a match to decide the series at The Oval. Grimmett proved the decisive bowler as Australia regained The Ashes with victory by 562 runs, which, more than 70 years on, is still the second largest margin of victory in terms of runs in any Test match.
O'Reilly was the leading Australian bowler of the tour, taking 28 Test wickets at an average of less than 25, while Grimmett took 25 wickets at just under 27 runs apiece. Australia's other Test bowlers took only 18 wickets between them. On the tour as a whole, O'Reilly headed the tourists' averages, with 109 wickets at 17.04, which meant that he also topped the averages for the whole English cricket season. In the matches against the English counties, he took 11 wickets in each of the games against Leicestershire and Glamorgan, and in the match against Somerset, after Hans Ebeling took the first wicket, he took the remaining nine for 38 runs, and that proved to be the best innings figures of his career. He was named as one of the Wisden Cricketers of the Year in 1935 for his deeds on tour.
O'Reilly played little state cricket for New South Wales in 1934–35, and none at all the following season, when he was selected for the Australian tour to South Africa. The tour was another triumph for the leg-spin attack of O'Reilly and Grimmett, but O'Reilly was slightly overshadowed by his team-mate in the Tests. With 44 wickets, Grimmett set a new record for the number of wickets by an Australian in a Test series, and he raised his Test career total to 216 wickets, beating the then world record of 189 by Englishman Sydney Barnes. O'Reilly took 27 Test wickets at an average of just over 17 runs each: the other bowlers in the Australian team took 27 wickets between them. On the tour as a whole, O'Reilly came out ahead of Grimmett, with 95 wickets against Grimmett's 92, and an average of 13.56 against 14.80. O'Reilly also revealed hitherto undiscovered batting talents, making an undefeated 56 in the Fourth Test in Johannesburg, and putting on 69 for the last wicket with Ernie McCormick. It was the only time in his first-class cricket career that he passed 50.
Clarrie Grimmett was dropped from the Australian team after the South African tour, leaving O'Reilly as the hub of the Australian bowling attack for the MCC Ashes tour in 1936–37. O'Reilly responded by becoming the leading Australian wicket-taker in the series taking 25, with Bill Voce taking 26 for England. But O'Reilly's wickets were at increased cost — his average increased to 22 runs per wicket — and he took five wickets in an innings only once, in the First Test at the 'Gabba in Brisbane, which England won convincingly. The circumstances of the series determined O'Reilly's role: after England won the first two Tests, O'Reilly appeared to have been given the job not just of bowling the opposition out, but also of containing them, and he was criticised in Wisden for defensive bowling. Wisden even went as far as to describe it as "leg theory", though the resemblance with the tactics used in Bodyline is likely to have been restricted to accuracy and hostility, O'Reilly being nowhere close to Harold Larwood for pace. If the intention was to stifle England batsman Wally Hammond in particular, then it appears to have worked, but O'Reilly's figures for the series suggest he was consistent but not always penetrative. Morris Sievers, from fewer matches, outperformed his average; Leslie Fleetwood-Smith, a slow left-arm spinner, got more eye-catching individual figures, including 10 wickets in the victory at Adelaide. Whatever the methods, they were successful: having lost the first two Tests, Australia proceeded to win the final three to retain The Ashes they had regained in England in 1934, and O'Reilly's five for 51 and three for 58 were the best figures in the decisive Fifth Test in Melbourne.
In the 1937–38 season, O'Reilly returned to more regular state cricket, and New South Wales duly won the Sheffield Shield for the first time in five seasons. He took 33 wickets at an average of just over 14 runs each, and against South Australia at Adelaide he repeated his feat against Somerset in 1934, taking the last nine wickets of the first innings at a cost of 41 runs. This time, he followed up with five for 57 in the second innings.
O'Reilly's second and final Ashes tour to England as a player in 1938 again saw him as the most effective bowler in the team. His final record of 22 wickets at an average of 27 in the four Tests — one Test was rained off in its entirety — was marginally less than 1934, and in all matches he took 104 wickets at 16.59. In its report of the tour, however, Wisden's 1939 edition noted that "it was nothing short of remarkable that despite the moderate support accorded to him he bowled so consistently well and so effectively." Again, O'Reilly was often used defensively where there was no help from the wicket, but, Wisden added, "when... the wicket gave him the least encouragement he robbed the greatest batsmen of initiative, and was most destructive".
In a mainly high-scoring series, O'Reilly's greatest triumph was in the low-scoring Fourth Test at Headingley, where he exploited a difficult pitch to take five wickets in each innings as Australia secured the victory that enabled them to retain the Ashes. His match figures were 10 for 122. Almost as important was his score of 42 in the Lord's Test that enabled Australia to save the match: having been dropped by Eddie Paynter, he hit Hedley Verity for consecutive sixes to take Australia past the follow-on mark. On the debit side, his figures at The Oval, where England posted the then-record Test score of 903 for seven wickets, were three for 178 off 85 overs. Nevertheless, these compared favourably with Fleetwood-Smith's one for 298 off 87 overs.
O'Reilly rested from Sheffield Shield cricket in the 1938–39 season, but resumed playing fairly regularly for New South Wales in the next two seasons before competitive cricket was suspended in Australia for the Second World War. First-class cricket resumed in Australia in 1945–46, though the Shield competition was not held that season. O'Reilly captained New South Wales, though the emergence of Ray Lindwall and Ernie Toshack in the state side indicated a shift in emphasis away from spin and towards faster bowling.
O'Reilly's final first-class cricket came on a four-match tour by an Australian team to New Zealand, during which a four-day match — in fact it was all over inside two days — against a representative New Zealand side was played, later to be designated as the first Test between the two countries. New Zealand were outclassed, making 42 in their first innings and 54 in their second to lose by an innings and 103 runs. O'Reilly took five wickets for 14 runs in the first innings, and three for 19 in the second. It was his last Test and his last first-class game.
Despite the mutual admiration between Bradman and O'Reilly for their cricket skills, personal relations between the pair were strained. In Australian society at the time, sectarian tension existed between Catholics, mostly of Irish descent, of whom O'Reilly was one, and Protestants, like Bradman. Bradman was a non-drinker and a reserved character, often preferring to read quietly, rather than socialise or drink with his team-mates. Coupled with his on-field dominance, this led to perceptions that Bradman was cocky and distant from his team-mates. In the late 1930s, the Australian Board of Control summoned O'Reilly, Stan McCabe, Leo O'Brien and Chuck Fleetwood-Smith, all Catholics of Irish descent to a meeting to discuss the apparent schism in the team. Jack Fingleton, a trained journalist, was not invited to the meeting, but after the deaths of both Fingleton and O'Reilly, Bradman penned a letter in which he accused Fingleton of being the ringleader. O'Reilly's eventual departure also raised speculation that a purge had occurred. O'Reilly later became a journalist, and together with Fingleton, he often criticised Bradman. They were in the press box when Bradman was bowled for a duck in his final Test innings, when they were reported to have become hysterical with laughter. Despite their conflicts, a few years before his death O'Reilly wrote that, compared with Bradman, batsmen like Greg Chappell and Allan Border were mere "child's play". In 1995, after both Fingleton and O'Reilly had died, Bradman wrote: "With these fellows out of the way, the loyalty of my 1948 side was a big joy and made a big contribution to the outstanding success of that tour".
| Batting | Bowling | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Opposition | Matches | Runs | Average | High Score | 100 / 50 | Runs | Wickets | Average | Best (Inns) |
| England | 19 | 277 | 10.65 | 42 | 0/0 | 2587 | 102 | 25.36 | 7/54 |
| New Zealand | 1 | - | - | - | - | 33 | 8 | 4.12 | 5/14 |
| South Africa | 7 | 133 | 22.16 | 56* | 0/1 | 634 | 34 | 18.64 | 5/20 |
| Overall | 27 | 410 | 12.81 | 56* | 0/1 | 3254 | 144 | 22.59 | 7/54 |