Containers of hardy plants generally do not require much in the way of special protection over the winter in a zone as mild as 7. There are some exceptions - plants which may prefer very dry soil conditions might fair better if protected from the worst of the rains, etc. But clematis, hostas and other hardy perennials, trees and shrubs can be left out through the winter in a zone 7, provided the container is of sufficient size.

If your garage is unheated, then the plants can go back outside now. No need to to do this gradually unless the garage temps have been consistantly above 50F. If a sharp frost or sudden cold spell is predicted, then cover the pots at night. Grouping them together will also afford some additional protection.

My nursery is located in a zone 7b and operates all year long. Containerized hardy plants are left outside all year as well, including those as small as gallon sized perennials and 4" groundcovers. Winter damage is minimal and is usually associated with too much wet/too moisture retentive a container soil rather than cold damage. Wholesalers in the area also grow their containerized crops outdoors all winter as well.