Plantation of Munster
In 1584, Valentine Browne became involved in the Plantation of Munster. The Irish province of Munster had been devastated since 1569 by the Desmond Rebellions which ended on 11 November 1583 when Gerald FitzGerald, 14th Earl of Desmond, the rebel earl, was killed. The earl's extensive lands were forfeit and the government planned to grant them to English undertakers and repopulate them with English settlers. In July 1584, the government commissioned a survey of these lands. Sir Valentine and Henry Wallop were appointed to manage this task. Arthur Robyns was one of the surveyors. In a letter to William Cecil, Lord Burleigh, Elizabeth's chief adviser, dated 10 October 1584, Sir Valentine wrote that "the work was so difficult as to have extended over three years." He further wrote from Askeaton that he had "travailed hard in superintending the survey, passing through bogs and woods, scaling mountains, and crossing many bridgeless rivers and dangerous waters", waters in which he lost some of his horses, and was twice nearly lost himself; that his son had broken his arm, and that "the service was so severe that many of the men had fallen sick". He described the towns and villages as ruined, and wrote that "not one of thirty persons" was left alive after the famine caused by crop destructions, and "those for the most part starvelings". Desmond's lands, thus nearly void of inhabitants, were, however, "replenished with wood, rivers, and fishings". Sir Valentine's survey divided the escheated lands into 35 seignories.
While living at Ross Castle near Killarney, Sir Valentine was in April 1585 elected MP for County Sligo in the Irish parliament of 1585/1586.
In 1586 He was elected MP of Berwick-upon-Tweed for the English Parliament of 1586, which submitted a petition demanding the execution of Mary Stuart, Queen of Scots.
In 1587 Sir Valentine returned to Ireland and applied for one of the seignories. He was granted Currans (in Kerry) in the early 1587 allotment, but this seignory was finally given to Charles Herbert and he was provisionally given the neighbouring seignory of Molahiffe instead. Molahiffe consisted of the territories of Onaght and Coshmaine, which had belonged to two vassals of Donald McCarthy, 1st Earl of Clancare who had sided with the rebels and died in the war. Clancare successfully claimed the lands for himself and then at a meeting with Sir Valentine in London on 28 June 1588 mortgaged them to him for about £600. Sir Valentine ended up owning 6,500 acres (26 km2) of land in County Kerry alone, in addition to earlier grants including the village of Hospital, County Limerick. He built a castle near this village, called Kenmare Castle. In 1588 when the Spanish Armada was menacing the coasts, he commanded a company for Ireland's defence.