What you can draw in with a specific antenna is a function of several things, one is how well tuned the antenna is, second is what direction the antenna is facing and how easily the antenna can get a signal. 

Most 4 bay antennas are pretty good, they have a fairly large surface area and a reflector that improves the signal. 

From Oshawa if you face the antenna at Toronto you should pick up the Toronto stations, but may not pick up Buffalo very well.  This can be solved by rotating the antenna to a different position.  If the antenna is accessable then this is easy, otherwise you need a rotor of some kind. 

The more stuff the signal needs to go through the less signal your going to get, if the station is to the South West and the TV is in the North East part of the house, your going to get less signal then if the antenna is in the South West corner of the house, or outside.  Generally the higher the antenna, the more signal you can get, this is why older TV antennas from the 1950's were generally on masts that were above the roof peak.