Right now, I'm giving my Nanday Conure "Ruby" a mix of Roudybush Maintenance, Harrison's High Potency and a few Harrison's Power Treats, the later crushed because they come in only one size, too big for conures. The reason for the mix is because Ruby loves Roudybush, but I think that Harrison's is probably even better for him. Mixing them up gets him to eat at least some of the Harrison's along with the Roudybush. Eventually, I am hoping he'll convert to Harrison's entirely. At that point, I'll probably still give him Roudybush once in a while, as a treat.
Both
Roudybush and
Harrison's describe how to gradually convert one's birds over to a pellet diet. Visit their websites for more info.