In a large skillet cook and stir bacon over medium heat until crisp. Remove with slotted spoon, drain on paper towels. Cook and stir mushrooms, onions and peppers in bacon drippings until tender. Using slotted spoon, remove to a small bowl, cool completely. Stir in bacon

In a large bowl, combine beef, steak sauce and season salt, mixing lightly but thoroughly. Shape into 16 thin patties. Top 8 of the patties with cheese, folding over cheese to fit within 3/4 inch of edge. Spread with mushroom mixture. Top with remaining patties, pressing edges to enclose filling.

Grilled stuffed burgers, uncovered, over medium-high heat for 5 to 6 minutes on each side or until a thermometer inserted in meat portion reads 160°.