Ingredients

1   (16-ounce) can dark red kidney beans, drained
1   (14.5-ounce) can cut green beans, drained
1   (14.5-ounce) can cut golden wax beans, drained
1 cup sliced fresh mushrooms
1/2 cup chopped red bell pepper
2 tablespoon minced red onion
1/2 cup vegetable oil
3 tablespoon white wine vinegar
1 tablespoon Dijon mustard
2 tablespoon Greek seasoning

Directions

In a medium bowl, combine first 6 ingredients. 

In a small bowl, whisk together oil, vinegar, mustard, and Greek seasoning. Pour over bean mixture; cover and chill 4 hours, stirring occasionally.