marinated cucumber salad recipe

2 medium cucumbers, thinly sliced
1 medium onion, cut into rings
2 cups thinly sliced carrots
1/2 cup sliced celery
1 cup vinegar
1/4 cup vegetable oil
3/4 cup sugar
1 tsp celery seeds
1 tsp salt
1/4 tsp ground black pepper
Lettuce leaves

Combine first 4 ingredients in a shallow dish; set aside. Combine next 6 ingredients, mixing well; pour over vegetables, tossing lightly. Cover and chill 8 to 10 hours. Drain and serve in a lettuce lined bowl.