Step 1

In a large skillet, heat 1 tablespoon oil over medium-high heat. Add mushrooms and onion; cook and stir until crisp-tender, 6-8 minutes. Add garlic, thyme, oregano, 1/4 teaspoon salt and 1/4 teaspoon pepper; cook 1 minute longer. Transfer to a large bowl; set aside.

Step 2

In the same skillet, heat remaining 1 tablespoon oil over medium high heat. Add steak, remaining 1/4 teaspoon salt and 1/4 teaspoon pepper; cook and stir until no longer pink, 4-5 minutes. Stir in cream cheese, 1-1/2 cups pepper jack cheese and onion mixture just until cheeses are melted. Remove from heat.

Step 3

Cut and discard tops from peppers; remove seeds. Fill with steak mixture. Place trivet insert and 1 cup water in a 6-qt. electric pressure cooker. Set peppers on trivet. Lock lid; close pressure-release valve. Adjust to pressure-cook on high for 10 minutes. Quick-release pressure. Sprinkle peppers with remaining 1/2 cup pepper jack cheese; cover and let stand until cheese is melted, about 5 minutes.