由1450年至1690年間，大部分立法事宜均由國會下轄之「法案委員會」（Lords of the Articles）處理。委員會本身由三級代表選出，以草擬法案並交由全體議會確認。由於委員會長年由親王派成員把持，過去歷史學家一般將其視作橡皮圖章。[13]不過，最近有部分歷史學家對此傳統觀點提出質疑，認爲法案委員會成員之多，意味著操縱委員會並不比操縱全體議會為容易。他們認為法案委員會只是擔當類似現代國會中專責委員會的角色，由熟悉法律的議員組成，以處理繁瑣的草擬過程。法案委員會因光榮革命於1690年被廢除。[14][15]
雖然蘇格蘭王國國會在1235年成立，直至1286年前史料對其描述不多，只知道其已經具有政治和司法職能。當亞歷山大三世在1286年去世後繼位的挪威女孩瑪格麗特並未成年，國會對護國主會議（英語：Guardian of Scotland）的支持為護國主會議出任攝政提供正當性。當約翰·巴里奧在六年後登基時，國會已發展成熟，並被巴里奧用以抗衡英格蘭國王愛德華一世對蘇格蘭的干預。雖然國會在巴里奧被廢後一度失去其影響力，但因羅伯特一世登基後再度召開國會而不致被廢。羅伯特在位期間大部分重要法案均於國會發表。
到中世紀末期時，騎士及地主階級地位逐漸上升，並透過選舉市鎮代表的方式參與議會運作。[19][20][21]國會權力也同時大爲擴張，君主除了在國會同意後才能徵稅外，其他事宜如司法、外交政策和戰爭等，勿論是否與政治、宗教、社會或經濟有關，均需國會同意才能實施。[22]國會大部分立法事宜均是交由下轄之法案委員會（Lords of the Articles）處理。其由三級代表選出，以草擬法案並交由全體議會確認。[22]
如同時代的其他議會，蘇格蘭王國國會在十六世紀的召開次數與十五世紀相比減少許多，若非1513年起的數次攝政，國會的權力可能會全數轉移至君主。[25]這段時期君主亦改以三級會議（英語：Convention of the Estates of Scotland）通過法案來取代國會。與國會相比，召集三級會議所需之時間更短，因此應對危機時更為迅速。不過三級會議每次只能處理單一議程，相比國會更抗拒賦予君主徵稅的權力。[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J. M. Goodare, 'Parliament and Society in Scotland, 1560–1603' (Unpublished Edinburgh University Ph.D. Thesis, 1989)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)
