Speculation raged ahead of Rangers' Scottish Championship fixture at Queen of the South that McCoist had offered to step down after three and a half turbulent years in charge at Ibrox.
McCoist refused to address the speculation after losing that clash 2-0, but Rangers have now confirmed to the London Stock Exchange that McCoist has quit.
The former Rangers striker will see his pay "increase significantly" through his notice period, though the club confirmed they will look to negotiate terms with McCoist.
Rangers' statement confirmed: "The Company announces that Alastair McCoist, manager of the first team squad, has resigned.
"His service contract dated 28 December 2010, which was subsequently amended, has a 12 month notice period ("Notice Period").
"The Directors will hold discussions with Mr McCoist to seek an amicable solution in the best interests of the Company, and expect to be in a position to make a further announcement before the end of the week.
"During the Notice Period, Mr McCoist's salary will increase significantly to £750,000 per annum."
Having seen Rangers banished to the bottom tier of Scottish football due to financial irregularities, McCoist led the club to consecutive promotions from League Two and League One.
However, Rangers have found life in the second tier tougher, and they sit nine points off the pace set by leaders Hearts, though McCoist's decision to leave is thought to be fuelled by continued turmoil off the pitch.
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