He became a clerk of assize on the Oxford Circuit in November 1660 and by 1663 had become successful enough to purchase property at Talton in Worcestershire and Honington in Warwickshire, where he began rebuilding a manor house.

In 1690 the 2nd Parliament of King William III and Queen Mary II was called but Parker's campaign for a third re-election was unsuccessful and he removed himself from the contest a few days before the poll for Evesham was completed.

[1] Parker's work on these issues made him popular with his constituents and he was re-elected for Evesham for the 4th Parliament of King William III later in the same year, described at the time as a "Country" supporter.

When the 5th Parliament of King William III was called in 1701 Parker chose not to run for re-election again and concentrated on matters closer to home, being elected a deputy lieutenant for Warwickshire.

In December the 6th Parliament of King William III was called but again Parker chose not to participate, and he instead supported the successful candidacy of his son Hugh for the Evesham seat.

Despite this he continued to have a say in local politics; he supported the parliamentary candidacies of William Bromley in 1705 and Sir Thomas Cookes Winford, 2nd Baronet (another son-in-law) in 1707, and it was estimated that he controlled between 60 and 80 votes.