Oldhall was with the Duke of York in Wales in September 1450; was returned to parliament for Hertfordshire on 15 October of the same year, and on 9 November following was chosen Speaker of the House of Commons. Indicted in 1452 for complicity in the insurrection of Jack Cade and the subsequent rebellion of the Duke of York, he was found guilty, outlawed and attainted on 22 June. He took sanctuary in the chapel royal of St. Martins-le-Grand, where he remained in custody of the king's valet until after the First Battle of St Albans on 22 May 1455, but obtained his release and the reversal of his outlawry and attainder on 9 July. He was again attainted in November 1459 as a fautor and abettor of the recent Yorkist insurrection; but on the accession of Edward IV of England the attainder was treated as null and void.