OAKVILLE, Ont. - The head of Tim Hortons has left his role at the company effective immediately, and Canada's No. 1 coffee chain says it will begin a search for his successor immediately.

Don Schroeder will no longer serve as president and CEO, after two decades working for the company, the Tim Hortons (TSX:THI) board announced on Wednesday.

The board said that it decided that a change at the top is best for the company at this time. In the meantime, executive chairman Paul House, who has previously held the position of president and CEO, will once again take on the role on an interim basis.

"Don Schroeder has made significant contributions to Tim Hortons during his 20 years of service, and although a transitional arrangement could not be reached, we appreciate his leadership as president and CEO since his appointment in 2008," House said in a release.

The move comes almost two weeks after Tim Hortons delivered underwhelming first-quarter results that missed analyst expectations by three cents per share. That sent the company's stock tumbling, as concerns grew over its strategy for future growth, particularly in the United States where results haven't been as robust as the company once hoped.

Shares of the company were down 1.4 per cent, or 66 cents, to $45.17 in early trading at the Toronto Stock Exchange.

"We have a talented, experienced and highly capable executive group, and we will continue to drive execution of our established strategic growth plans and initiatives, which are designed to capitalize on market opportunities, as the board concludes the process to appoint a new CEO," House added.

The board said it was already considering a succession scheme for the CEO position as part of its strategic planning.

House has worked for Tim Hortons for more than 25 years, and held the role of president and chief operating officer in the mid-'90s as well as CEO on a temporary basis in 2005 as Schroeder transitioned into the job.

Tim Hortons has been in the hot seat in recent months after it became increasingly clear that the company's once-ambitious expansion into the United States wasn't necessarily going according to plan. The restaurant operator announced late last year it would shut down 54 locations in New England where it was losing money.

The closures were considered by many as a sign that Tim Hortons has run into major problems convincing Americans to buy its products, even after a splashy rollout of locations in high-trafficked spots like Times Square and Broadway in Manhattan.

In the most recent quarterly results, the company's same-store sales, or results for stores open at least a year, rose two per cent in Canada and 4.9 per cent in the United States. Canadian same-store sales were affected by higher redemptions for food and beverage prizes in the company's popular Roll Up the Rim to Win promotional contest.

Based in Oakville, Ont., Tim Hortons is Canada's biggest restaurant chain and the fourth-biggest in North America with more than 3,700 restaurants on the continent.