[17] The role of premier is not defined by statute, except by reference to higher entitlement to pay under the Executive Council Act.

As a member of cabinet, the premier is subject to the constitutional norm of individual ministerial responsibility, and is therefore expected to either be a Member of Provincial Parliament, or to quickly seek election to a seat in the legislature so that they may answer questions from the legislature in debate and question period.

Due to Ontario being a unicameral Westminster-style parliamentary government, the premier is typically the leader of the party which has the most support in the Legislative Assembly at that time.

Premiers hold office by virtue of their ability to command the confidence of the elected Legislative Assembly.

They typically sit as a member of Provincial Parliament (MPP) and lead the largest party or a coalition in the assembly.

Once sworn in, the premier holds office until their resignation or is removed by the lieutenant governor after either a motion of no confidence or defeat in a general election.

While the legislature may be dissolved for an election, the executive council continues serving under the caretaker convention, where government ceases to make major policy decisions except in response to disaster.

[20] The premier has been a continuous role since 1914, when there was a one-week vacancy in the office between James Whitney and William Howard Hearst.

[22] The premier plays multiple functions in the Ontario political system, mirroring most conventions of the federal level of Canadian government.

For example, it expected due to individual ministerial responsibility that each minister shall be an MPP, or shall swiftly seek a seat in the legislature by participating in a by-election.

It is also expected that there be some level of diversity within the cabinet, on a geographic basis as much as the number of MPPs in the governing party permits.

[25] A premier will generally select ministers based on many factors including diversity, rewarding past or expected loyalty, satisfying factions within their party, creating a narrative or symbolism about choices, and primarily by who they expect can competently make decisions in a politically successful manner.

[26] The premier also has large amounts of discretion over the creation, composition and dissolution of cabinet committees, except the Treasury Board, which has its existence and size established by statute.

This typically follows heavy preparatory work on the part of minister's offices and staff, as well as civil service policy analysts.

The premier is also bound by individual ministerial responsibility, and is expected to present themselves to question period on an at least occasional basis.

[36] The premier sets the tone for communications through all of government, with a leader typically attempting to cultivate a "brand", to varying levels of success.

Budgets, and other funding bills are always confidence votes as are the address in reply to speech from the throne that happen at the beginning of each parliamentary session.

[39] In extraordinary circumstances, the lieutenant governor may refuse this advice, but in general, there is great latitude given to prime ministers in requesting prorogation.

For example, the Ontario government recently was involved in a court case regarding the constitutionality of the carbon pricing regime.

Such an issue was pertinent in 2021, where Ontario is the sole province not to sign on to a vastly expanded federal financial commitment under its childcare accords.

Even while another person may hold that ministerial title, the premier is still likely to serve a major intergovernmental affairs role through their presence at first ministers conferences.

While Leslie Frost served for a short time as the minister for the Department of Economics (functionally Minister of Finance), a premier is unlikely to take on a more senior challenging portfolio such as finance, health or education due to their complexity and time demands.

In Ontario, examples of taking more junior files include Kathleen Wynne serving concurrently as Premier and Minister of Agriculture and Food for one year.

Since Frost's short time in his ministry, no other premier has taken on a ministerial role except for that of intergovernmental affairs.

The Cabinet Office plays a coordination role, attempting to harmonize procedures between ministries where possible, as well as monitoring key performance indicators and departmental plans.

The salary of the premier is determined by their pay as an MPP, if they hold a seat in the legislature, which is governed by the Legislative Assembly Act.

[55] In addition, the Executive Council Act establishes a premium of 79.3% above the MPP salary, 37% for their role as Premier and the remaining 42.3% if they retain the portfolio of Intergovernmental Affairs.