由1450年至1690年间，大部分立法事宜均由国会下辖之“法案委员会”（Lords of the Articles）处理。委员会本身由三级代表选出，以草拟法案并交由全体议会确认。由于委员会长年由亲王派成员把持，过去历史学家一般将其视作橡皮图章。[13]不过，最近有部分历史学家对此传统观点提出质疑，认为法案委员会成员之多，意味着操纵委员会并不比操纵全体议会为容易。他们认为法案委员会只是担当类似现代国会中专责委员会的角色，由熟悉法律的议员组成，以处理繁琐的草拟过程。法案委员会因光荣革命于1690年被废除。[14][15]
虽然苏格兰王国议会在1235年成立，直至1286年前史料对其描述不多，只知道其已经具有政治和司法职能。当亚历山大三世在1286年去世后继位的挪威女孩玛格丽特并未成年，国会对护国主会议（英语：Guardian of Scotland）的支持为护国主会议出任摄政提供正当性。当约翰·巴里奥在六年后登基时，国会已发展成熟，并被巴里奥用以抗衡英格兰国王爱德华一世对苏格兰的干预。虽然国会在巴里奥被废后一度失去其影响力，但因罗伯特一世登基后再度召开国会而不致被废。罗伯特在位期间大部分重要法案均于国会发表。
到中世纪末期时，骑士及地主阶级地位逐渐上升，并透过选举市镇代表的方式参与议会运作。[19][20][21]国会权力也同时大为扩张，君主除了在国会同意后才能征税外，其他事宜如司法、外交政策和战争等，勿论是否与政治、宗教、社会或经济有关，均需国会同意才能实施。[22]国会大部分立法事宜均是交由下辖之法案委员会（Lords of the Articles）处理。其由三级代表选出，以草拟法案并交由全体议会确认。[22]
如同时代的其他议会，苏格兰王国议会在十六世纪的召开次数与十五世纪相比减少许多，若非1513年起的数次摄政，国会的权力可能会全数转移至君主。[25]这段时期君主亦改以三级会议（英语：Convention of the Estates of Scotland）通过法案来取代国会。与国会相比，召集三级会议所需之时间更短，因此应对危机时更为迅速。不过三级会议每次只能处理单一议程，相比国会更抗拒赋予君主征税的权力。[26][27]
Mann, Alastair, "A Brief History of an Ancient Institution: The Scottish Parliament", Scottish Parliamentary Review, Vol. I, No. 1 (June, 2013) [Edinburgh: Blacket Avenue Press]
Brown and Tanner, passim; R. Tanner, The Late Medieval Scottish Parliament, passim; K. Brown and A. Mann, History of the Scottish Parliament, ii, passim
Kidd, Colin Subverting Scotland's Past: Scottish Whig Historians and the Creation of an Anglo-British Identity 1689–1830 Cambridge University Press (2003) p. 133
The "fourth estate" argument is primarily favoured by Julian Goodare, and disputed by Keith Brown. A summary of the most recent research can be found in Brown and Mann, History of the Scottish Parliament, ii.
K. M. Brown and R. J. Tanner, The History of the Scottish Parliament volume 1: Parliament and Politics, 1235–1560 (Edinburgh: Edinburgh University Press, 2004), ISBN0-7486-1485-0, pp. 1–28.
R. A. Mason, Scots and Britons: Scottish Political Thought and the Union of 1603 (Cambridge: Cambridge University Press, 2006), ISBN0-521-02620-2, p. 82.
A. I. Macinnes, Union and Empire: The Making of the United Kingdom in 1707, Cambridge Studies in Early Modern British History (Cambridge: Cambridge University Press, 2007), ISBN0-521-85079-7, p. 68.
K. M. Brown and R. J. Tanner, The History of the Scottish Parliament volume 1: Parliament and Politics, 1235–1560 (Edinburgh, 2004)
A. A. M. Duncan, 'Early Parliaments in Scotland', Scottish Historical Review, 45 (1966)
J. M. Goodare, 'Parliament and Society in Scotland, 1560–1603' (Unpublished Edinburgh University Ph.D. Thesis, 1989)
C. Jackson, 'Restoration to Revolution: 1660–1690" in Glenn Burgess (ed.), The New British History. Founding a Modern State, 1603–1715, (London, 1999), pp. 92–114.
Alan R. MacDonald, 'Ecclesiastical Representation in Parliament in Post-Reformation Scotland: The Two Kingdoms Theory in Practice', Journal of Ecclesiastical History, Vol. 50, No. 1 (1999)
N. A. T. Macdougall, James IV (Edinburgh, 1989), chapter 7
"An Introduction to the pre-1707 Parliament of Scotland" (Based on a paper to Staff Development Conference for History Teachers, National Museum of Scotland, 25 May 2000 by Dr. Alastair Mann, Scottish Parliament Project, University of St. Andrews).
R. Nicholson, Scotland, the Later Middle Ages (Edinburgh, 1974), chapter 15
I. E. O'Brien, 'The Scottish Parliament in the 15th and 16th Centuries' (Unpublished Glasgow University Ph.D. Thesis, 1980)
R. Rait, The Parliaments of Scotland (Glasgow, 1924)
R. J. Tanner, The Late Medieval Scottish Parliament: Politics and the Three Estates, 1424–1488 (East Linton, 2001).
R. J. Tanner, 'The Lords of the Articles before 1540: a reassesment', Scottish Historical Review, LXXIX (October 2000), pp. 189–212.
R. J. Tanner, 'Outside the Acts: Perceptions of the Scottish Parliament in Literary Sources before 1500', Scottish Archive (October, 2000).
R. J. Tanner, 'I Arest You, Sir, in the Name of the Three Astattes in Perlement': the Scottish Parliament and Resistance to the Crown in the 15th century', in Social Attitudes and Political Structures in the Fifteenth Century, ed. T. Thornton (Sutton, 2000).
C. S. Terry, The Scottish Parliament: its constitution and procedure, 1603–1707 (Glasgow, 1905)
J. R. Young, The Scottish Parliament 1639–1661 (Edinburgh, 1997)
