In a medium pan heat ground beef over medium heat till browned. Add in vegetables, pepper and garlic. Continue heating till vegetables and garlic are cooked. Add in mushroom soup and heat for another five minutes till mixture is warmed.
While ground beef is cooking. Heat a large pot of water over high and add in potatoes. Boil till potatoes are softened. Mash potatoes and add in milk, seasoning salt and butter till smooth.
Put ground beef mixture into a 9 x 9" dish. Top with mashed potatoes and heat in oven uncovered for 30 minutes.
If you would like the top of the pie to be browned more you can broil in the oven for the final 5 minutes of cooking.