Cut 1 red & 1 yellow bell pepper and 1 red onion into thin slices. Finely chop 2 cloves garlic.
Pour 1 Tbsp oil in a large sauté pan over med-high heat. Add garlic, bell peppers & onion, sauté for ~10 minutes.
Add 1# stir-fry beef and 2 Tbsp taco seasoning, cook ~5 minutes or until just cooked.
Serve fajitas in warmed corn tortillas (or lettuce wraps) with guacamole and lime slice on the side.