Pat's King Of Steaks Philly Cheesesteak

Ingredients

• 1 large onion, sliced
• ketchup (optional)
• 1 small green bell pepper, sliced (optional)
• easy cheese, or other processed cheese sauce
• 1 small red bell pepper, sliced (optional)
• 6 tablespoon canola oil, divided
• 4 crusty italian rolls, split
• 1 1/2 pound beef rib-eye steaks, thinly sliced
• 1/2 pound sliced fresh mushrooms (optional)