Ham and Potatoes Au Gratin

This is a recipe I've made for many years.  It is comfort food to me.

Ham and Potatoes Au Gratin
1/2 c. chopped onion
1/2 c. chopped green pepper
4 Tbsp. butter or margarine, divided
5-6 c. diced, peeled potatoes, cooked
2 c. ham, cubed
1/2 c. mayonnaise
3 Tbsp. flour
1 1/2 c. milk
1 c. shredded cheddar cheese
1/8 tsp. garlic powder
salt and pepper

In a skillet, saute onions and green pepper in 1 Tbsp. butter until tender. Combine onions and pepper with potatoes, ham and mayonnaise; pour into a 9x13 baking dish.  In a saucepan, melt remaining butter, stir in flour, and garlic powder until smooth, gradually add milk.  Bring to a boil, cook and stir for 1 min.  Stir in cheese just until melted and add salt and pepper to taste.  Pour over potato mixture.  Cover and bake at 350 for 45 min. or until bubbly. 

Notes: I have used a bag of cubed hash brown potatoes in this with decent results.

Jenny