I love brewing my Belgian Wit, and I have switched to using fresh orange peel, I grind the skin down, but I do not get into the pith (white part).
For a 10 gallon batch I will use 2 oz with 10 min left in the boil, and an additional 1 oz in the secondary, like a dry hop.
The orange flavor comes out very well, but not over powering.
I would also like to take this opportunity, to caution you, to be VERY careful when grinding your coriander. I only use 1/2 oz for 10 gallons, and when I crack my coriander, I like to get them into halves, or sometimes 1/4 pieces, anything beyond that can overpower the beer.
Hopefully I am not telling you something that you already know.
I also throw in 1/2 oz of cracked pepper corns, it really adds a nice bite, and flavor to accompany the coriander.
I have my recipe under my name if you want to take a look.
Hope this helps,
Josh