Heat oil in a large nonstick skillet over medium heat.
Add bell peppers and onion; cook, stirring occasionally, for 5 to 6 minutes, or until onion is translucent and peppers are tender.
Add garlic; cook, stirring frequently, for 1 minute.
Add beef, chili powder, cumin, pepper flakes, and salt; cook, stirring occasionally, for 7 to 8 minutes, or until meat is no longer pink.
Add salsa; cook, stirring frequently, for 2 to 3 minutes, or until heated through.