Cut the sirloin steak tips into bite-sized pieces and place them in a zip lock bag.

In a small bowl, mix together the olive oil, red wine vinegar, soy sauce, Worcestershire sauce, brown sugar, minced garlic, and red pepper flakes. Pour the marinade into the zip lock bag with the steak tips and massage the bag to make sure the steak pieces are evenly coated. Marinate for at least 8-24 hours.

Heat a large skillet or ribbed grill pan over medium-high heat. Remove the steak tips from the marinade and discard the excess marinade.

Add the chopped onion and red bell pepper to the skillet and cook until the onions are caramelized, stirring occasionally. Remove the onions and peppers from the skillet and set aside.

Add the steak tips to the skillet and cook for 2-3 minutes on each side or until browned on the outside and pink on the inside.

Add the sliced mushrooms and cooked onions and peppers back to the skillet with the steak tips. Cook for an additional 2-3 minutes or until the mushrooms are cooked through.

Serve the IHOP-style steak tips hot and enjoy!