Marinated Cucumbers

6 medium cucumbers, thinly sliced
1 medium onion, sliced
1 cup white vinegar
1/4 to 1/3 cup sugar
1/4 cup olive oil
1 teaspoon salt
1 teaspoon dried oregano
1/2 teaspoon garlic powder
1/2 teaspoon dried marjoram
1/2 teaspoon lemon-pepper seasoning
1/2 teaspoon ground mustard

In a large bowl, combine the cucumbers and onion. In a jar with a tight-fitting lid, combine the remaining ingredients; cover and shake well. Pour over cucumber mixture; toss to coat. Cover and refrigerate at least 4 hours.