In 1558 Bromley was MP for the Shropshire borough of Bridgnorth in the last parliament of Mary's reign. At this point he had not completed his education, although he was about 28 years old and a recognised lawyer. He probably owed his election mainly to family connections. His mother's family had numerous links in the Bridgnorth area. The High Sheriff of Shropshire had a considerable say in elections, and in that year was Richard Newport, son-in-law of the chief justice Thomas Bromley and another Inner Templar. The town's elector's, a council of 14 aldermen and bailiffs, had a predilection for lawyers. Their other choice was John Broke, a young Middle Templar and the son of the Shropshire jurist Robert Broke. However, the election seems to have been delayed, perhaps for want of nominations, until 18 January, only two days before the opening of parliament.