Please clarify...first you say the box has a red, black, and white wire, but then a few sentences later you refer to two black wires. How many wires of what colors enter the box?

It sounds like you have a 3 way switch? If you don't then below should work if I am reading it correctly.

You should have 3 black wires in your box. One is your main power in, one is your continuation to the garage and one is the overhead light. You need to twist your line in and your garage line together with a 6" chunk of wire that you then run to your switch. The black line running to your overhead light should then be attached to the other terminal on the switch. Your white wires should be twisted together. I still don't understand why you have a red line but if it was capped off then leave it capped off. To find out which black wire is which. Hook two up and make sure your white wires are together as well and then turn on the power and see what happens. If nothing turns on then the remaining black line is your power. If your garage light turns on or your light turns on then you know you have power and the line running to on of them. Mark each wire with a number to keep track and then turn off power and keeping one of the wires attach it the wire that wasn't attached before and then turn the power back on. If the lights don't work then wire you disconnected is power. If it does work then the line you kept is power and the other line goes to the light that turn on.