The Glorious Revolution didn't necessarily reduce the powers of the monarchy in favour of Parliament.

In theoretical and legal terms, it did, due to the Bill of Rights described in Blush Response's excellent writeup.

However, by granting Protestants toleration, it removed one area of conflict between the crown and Parliament, and the Bill in general brought in a new era of co-operation between the two institutions. This was enhanced by the guarantee of a regular income for the monarch; finance had been an area of conflict and ultimatums during the reigns of Charles I and James I. By creating more harmony between the king and Parliament, they were able to rule as the king-in-parliament, with the result that power for both increased.

William and Mary, and Anne after them, used their power in co-operation with Parliament. However, it was with the accession of the Hanoverians, George I and George II, that the crown began to lose power. Anne was the last monarch to use the royal veto on Bills in 1708. George I spoke no English and allowed his ministers to run the country; after 1717 he stopped attending cabinet meetings. In this way, he allowed power to slip into the hands of Parliament, a decline in royal power which contiued in the reigns of George II, III and IV.

While the Glorious Revolution theoretically marked a decrease in royal power in favour of Parliament, it took an incompetent monarch to put the theory into practice.