Vegetable and Cheese Chowder

1/3 cup quick or old fashion oats, uncooked
1 cup sliced celery
1/2 cup chopped onion
2 Tbsp. butter
2 cups milk
2 cups water
1 package (16 oz.)frozen mixed vegetables (can substitute canned or, even better, fresh vegetables of your choice - you would just need to cut the cooking time down a bit)
1 tsp mustard
1/2 tsp salt
1/8 tsp black pepper
2 cups (8 oz) cheddar cheese, shreaded

Place oats in food processor or blender; cover and process for 1 minute; set aside.
In a 4-quart saucepan or a dutch oven, saute celery and onion in butter until tender; blend in ground oats.
Gradually add milk and water; continue cooking over medium heat, stirring constantly, until thickened.
Reduce heat; add remaining ingredients except cheese.
Continue cooking over low heat for 10 minutes or until veggies are heated through.
Remove from heat; add cheese and stir till well blended.