Heat a medium-sized skillet over medium-high heat. Add the olive oil. Once oil is hot, add the onion and let them cook until translucent, about 5 minutes.
Meanwhile, place bite-sized pieces of meat in a resealable plastic bag and add the Montreal steak seasoning. Seal bag an gently shake to get meat coated. If, desired, add the 1/4 cup of breadcrumbs to the bag and shake until lightly coated.
Add the steak to the onions in the skillet. Cook until meat is no longer pink. Drain on papertowels and serve warm.