- 3 small yellow summer squash, thinly sliced
- 1 large sweet red pepper, cut into 1/4-inch strips
- 1 medium onion, chopped
- 1 tablespoon salt
- 1 cup sugar
- 3/4 cup white vinegar
- 3/4 teaspoon mustard seed
- 3/4 teaspoon celery seed
- 1/4 teaspoon ground mustard
- Place squash, pepper and onion in a colander over a plate; sprinkle with salt and toss. Let stand 1 hour to drain.
- In a large saucepan, combine remaining ingredients; bring to a boil, stirring to dissolve sugar. Add vegetables; return to a boil. Remove from heat; cool completely.
- Transfer to a covered container; refrigerate, covered, at least 4 days before serving. May be stored in refrigerator up to 3 weeks.