Heat the oil in a large fry pan over medium-high heat.
Fry the halloumi for 2-3 minutes on each side until golden. Take off the heat and set aside on a plate.
Add the onions to the same pan and cook for a few minutes until soft and translucent then add the fajita seasoning and capsicums. Stir well until well coated with the spice. Add extra olive oil if required and cook for a few minutes until the capsicums are tender.
Return the halloumi to the pan and cook for another 1-2 minutes. Stir gently.
Serve immediately with warm tortillas and serving suggestions.