HEAT oil in large skillet on medium-high heat. Add mushrooms; cook and stir 3 minutes or until tender. Cool completely.
MIX ground beef and Seasoning Mix until well blended. Divide into 8 portions. Shape into thin patties. Place about 1 tablespoon each of the mushrooms and cheese in center of each of 4 patties. Top with remaining patties, pinching edges to seal filling. If necessary, lightly flatten with spatula.
GRILL over medium heat 4 to 6 minutes per side or until burgers are cooked through (internal temperature of 160°F).
SERVE burgers on rolls topped with remaining mushrooms.