Crosbie came of a well established if somewhat impoverished Kerry family, of whom the most influential member in his day was his cousin John, 2nd Earl of Glandore, who returned him to the Irish parliament for the county. Crosbie got himself into difficulties on the Union question, his disgruntled absence from the debates in January 1799 being construed as hostility. Glandore, a firm unionist, made him toe the line by the following year. In August 1800, too late as he found out, Glandore applied to the Castle for a place as reward for his docile cousin. To make up for it, he offered to resign his colonelcy of the Kerry militia in Crosbie’s favour and in 1801, as a result of financial embarrassments caused by ‘engagements into which he had entered, in the expectation of Lord Glandore’s resignation’, Crosbie induced Glandore to fulfil the promise: not without souring their relations, for Glandore was most reluctant to surrender the colonelcy and had failed on further application to secure a place for Crosbie from the lord lieutenant; nor would he himself settle a pension of £300 p.a. on Crosbie’s wife.
After Crosbie’s re-election in 1802 Glandore tried to get back the colonelcy by obtaining a place for Crosbie, who also applied but courted failure by asking for one compatible with Parliament. Glandore was further chagrined when Crosbie was appointed a governor of Kerry conjointly with him in 1803. On 3 Oct. 1805 he wrote to Pitt claiming back his colonelcy on the strength of a report that Crosbie was to get a place, and made it clear that he would not support Crosbie in future.
Crosbie had given an undistinguished support to government in the House. He never, apparently, uttered in debate. He was reported as following Glandore’s line, but ‘no positive assurance of attendance’ was a typical comment on him, 29 Dec. 1804, at which time the chief secretary gloomily forecast that he would have to dole out a Kerry job to get Crosbie’s vote. On 30 Apr. 1805 Crosbie was reported to be at his house in Kerry: ‘he is in very necessitous circumstances and will not ... stir from his home without some inducement to do so.’ One such inducement of another kind was the Catholic cause, which Crosbie supported by his vote, 14 May 1805: he was pledged to it and would have risked his seat by omitting to do so. In May 1806 he was reported by the Grenville ministry’s chief secretary to be ‘very distressed in his circumstances. Ready to support but doubtful as to his succeeding on the next election.’
Without Glandore’s support, Crosbie stood no chance in 1806 and dropped out. In 1807 he offered with the countenance of the Portland ministry, to whom he promised support except on the Catholic claims (unless they infringed on the royal prerogative), but withdrew to await a more favourable opportunity. The inheritance of £3,000 p.a. from an aged uncle improved his prospects and, although his enemies labelled him a ‘plebeian boor’, he secured his election in 1812 as a ‘warm friend’ of government. This time he was particularly indebted to Lord Ventry for support, and the obtainment of a peerage promotion for the latter and a militia command for Ventry’s son became his chief demand in return for being, as the chief secretary admitted in July 1813, ‘a very constant attendant and has uniformly voted with us’.
While Crosbie’s only contrary votes were for the Catholic claims (13 and 24 May 1813, 30 May 1815, 9 May 1817 and 3 May 1819) he became less disposed to attend when his requirements were not met. Thus on 28 May 1814 he expressed ‘his zealous readiness to attend his parliamentary duty, if you required it, but his attendance will be peculiarly inconvenient’. He was told by the viceroy that he must attend and he agreed. On 26 Dec. 1815, disappointed at Ventry’s not being promoted, he was mortified: ‘I will say not a man in Ireland attended more regularly for them than I did’.
Crosbie secured his re-election in 1818, though he could not resist a hustings stratagem of offering government to return a second Member friendly to them if they granted Ventry’s peerage promotion. That he was still resentful is indicated by a report in March 1819 that he had gone to Ireland to recruit support for a projected group of independent Members prepared to quit ministers, but on 18 May he appeared in the government majority against Tierney’s censure motion and by 1820 he was secure in the possession of the county patronage.