Preheat air fryer to 350 degrees.

In a medium bowl, add brussels sprouts, avocado oil, salt, pepper, garlic, and balsamic vinegar. Toss gently until brussels are evenly coated.

Add brussel sprouts in a single layer to an air fryer basket lined with parchment paper, in a silicone basket, or lightly sprayed with oil.

Air fry for 6-7 minutes.

Add feta cheese and air fry for 5-6 additional minutes until brussel leaves are crispy and feta is golden brown and melted.

Preheat oven to 425 degrees (if using the oven).

In a medium bowl, add brussels sprouts, avocado oil, salt, pepper, garlic, and balsamic vinegar. Toss gently until brussels are evenly coated.

Add brussel sprouts in a single layer to a prepared baking sheet lined with parchment paper or lightly sprayed with oil.

Roast brussel sprouts for approximately 12 minutes, stirring halfway through.

Add feta cheese and continue roasting for 7-8 more minutes until feta cheese is melty and golden brown.