Brush chicken with olive oil, salt and pepper. Wrap in foil and bake in the preheated oven 1 to 1 1/2 hours, until internal temperature has reached 160 degrees F (70 degrees C).
Remove chicken from heat. Cool, debone and chop.
In a large bowl, mix chicken, mayonnaise and dill. Gently fold in grapes, mandarin oranges and sunflower seeds.
Spread the mixture on miniature croissants. Cover and chill in the refrigerator until serving.
