On 24 October 1259, towards the end of a session of parliament, the Provisions of Westminster were read out in Westminster Hall in the presence of King Henry III, many of his earls and barons and a large number of other people. The Provisions of Westminster were, by any reckoning, a major piece of legislation. No contemporary text of the Provisions numbers its clauses, but in the conventional modern enumeration first devised by William Stubbs and still used by scholars the Provisions consist of twenty-four clauses. The final text of the Provisions, as subsequently copied and sent out to the counties, and probably also as initially read out at Westminster, makes no direct mention of the session of parliament. It does, however, ascribe the making of the legislation to a meeting of the king and his magnates at Westminster (meaning a parliament) held a fortnight after Michaelmas (the week beginning 13 October) in the year of grace 1259 and in Henry III's forty-third regnal year. The date is probably the date parliament opened.

The Provisions directly reflect the exceptional political situation which existed at the time of their enactment, and the degree to which the king had agreed, or been compelled, to surrender the control of his administration to a group of his opponents, drawn from the baronage.