Slice squash, onions, and peppers into thin slices (do not peel squash). Place in large bowl, add 1/4 cup salt, cover with cold water. Let stand for one hour, use ice to keep cool or refrigerate. This step is VERY important – don’t skip it! After an hour or so, drain through a colander.

While vegetables are draining, combine the following in a pot large enough to hold the vegetables: sugar, vinegar, celery seed, pickling spice and mustard. Boil ingredients for three minutes, stirring occasionally, then add drained squash mixture. Simmer for three more minutes. Bring to a boil.

Pack in hot canning jars and fill to 1/2 inch of top of jar with juice. Process as for pickles. Makes 8-10 pints.