Jo Packer’s Pepper trilogy are the only books by her I have been able to find.  The covers, being by Peter Beigel are beautiful, but the contents of the only one I’ve read do not quite match up.  Gymkhana Trek is an adventure-with-ponies.  It’s a good comfort read, but it didn’t leave me longing to read the others in the series.

Pepper Leads the String
Herbert Jenkins, 1965, illus Juliette Palmer

No Pony Like Pepper
Herbert Jenkins, 1957, illus Peter Biegel

Gymkhana Trek
Herbert Jenkins, 1959, illus Peter Biegel

Many thanks to Susan Bourgeau for the picture.