What is the proper way to address a husband and wife when the husband is a Junior as an example Bill Jr and Peggy Smith?

I don't know the context of the question ... but if you are talking about a invitation for a wedding then ...

Formally for the envelopes on the letters :: "Mr. and Mrs. William Smith, Jr. "

informal ... Bill and Peggy (for when you are greeting them in the receiving line at the wedding.)

/R.