In a small bowl, whisk olive oil, soy sauce, sriracha, garlic powder, onion powder, red pepper flakes, parsley, brown sugar and salt.
Add sliced steak to another bowl, and mix in 1/2 of sauce mixture. Mix until all steak slices are coated. Cover with plastic wrap, and let it sit for 15 minutes.
Heat a large skillet over medium-high heat. Sear steak strips for 2 minutes on one side. then flip and sear on other side for 1 minute. The strips are thin, so do not overcook. Also, do not crowd skillet. Cook in batches if needed. Remove steak and let rest on a plate.
Reduce heat to medium, and add garlic. Sauté garlic for 1 minute. Add onion and bell peppers to skillet, and stir in remaining sauce mixture. Reduce heat low, and cover. Simmer for 7 minutes, stirring occasionally, to prevent sticking. Cook vegetables less or longer depending on desired tenderness.
Turn off heat and stir in cooked steak. Serve warm with side dish of choice. Rice or potatoes recommended.