Rub the turkey medallions with barbecue spice and sear in oil on both sides, sear for 3 minutes each, then wrap in aluminum foil and place in oven at 150°C for 15 minutes.
Saute onion in oil until translucent, then add mushrooms and sauté until nicely browned. Heat the mixed vegetables and arrange on a plate.
Pour the juices that land from the meat in the foil over the vegetables and garnish the turkey medallions with the mushrooms.