Dear Mike, I am relly sorry I have not got a map with me, so this is from memory, but to get to Wasaga Beach staying off the QEW and the 401 will require some fairly long detours (though pretty). My suggestion, for what it is worth, would be to take the QEW and the 401 to Toronto, then take the 400 north about halfway to Barrie, and then get off (there is a turn just at Canada's Wonderland -- you can't miss its disgustingness) and go north on the road that goes alongside the 400 to the east (I think it is 29) which is a nice drive. If you don't take the 400 it will be a lot longer than 90 minutes!!!
The roundabout route would be to head north along the Niagara Escarpment when you get to Canada (I don't know the road number, it may be highway 2) and head for Guelph and Elora (which is a pretty town, and a good place to stop for lunch). You could then follow the Grand River north for awhile. Then you need to head over to Collingwood. There are some nice drives around Creemore (Canadian beer country) and through the Beaver Valley towards Duntroon. When you get to Collingwood, Wasaga Beach is not far away. If you follow the line of the escarpment, you will get most of the pretty country. If you feel like hiking, the Bruce Trail goes the length of the escarpment -- and there are one or two very easy trails about 10 minutes drive from Wasaga beach in the Pretty River Valley.
I can give you lots more information if you need it, but I was worried about your deadline. If you aren't going for another day or two, I can get you chapter and verse.
Yours, Peter T.