And McCoist is unimpressed with Neil Doncaster's rationale that the stadium would not be ready following Rangers' potentially crucial League One clash with Dunfermline 24 hours earlier.
The Scottish Professional Football League chief executive announced on Wednesday that 60,000-seater Celtic Park would host the March 16 contest between Aberdeen and Inverness.
With Hampden being redeveloped for the Commonwealth Games, Ibrox was the only other stadium in the running and the 50,000 capacity would likely have been sufficient.
When asked if he was surprised Ibrox had lost out to Celtic Park, McCoist said: "Not surprised at all.
"I did say to the chief executive that if we were allowed to bet, which of course we're not, get a few quid on the cup final not being at Ibrox.
"I think obviously Neil, or indeed whoever is running the SPFL, made the decision and they'll stick by it."
If Rangers and Dunfermline keep winning League One games until they meet on March 15, then McCoist's men could clinch the title that day, meaning the game is highly likely to be televised.
Doncaster stated that would make it difficult for Ibrox to be prepared for a cup final broadcast by a different television station 24 hours later. Celtic are away at Kilmarnock on March 15.
But McCoist said: "I've worked with television long enough that I know these boys are unbelievable at their job in terms of de-rigging and setting up for games.
"Come on. That doesn't wash with me at all and I don't think it washes with you either."
Doncaster said: "Ibrox, we believe, has a game on the Saturday which is likely to be televised.
"And in those circumstances, with the televised game on Saturday lunchtime, there simply wasn't enough time to de-rig Ibrox in time for the Sunday game. So that's the key reason we have gone for Celtic Park."
The Scottish Football Association has already announced that Ibrox will host both William Hill Scottish Cup semi-finals and Celtic Park will stage the final.