The Orton-Gillingham (O-G) Approach is not a published program; rather, it is an “approach" that is considered to be "best practice" for intervention with people who are on the dyslexia spectrum.  Therefore, O-G is not tied to any published set of materials or any specific scope & sequence. You can read more about the distinction between an “approach” and a “program” on the website of the Academy of Orton-Gillingham Practitioners and Educators.

Various companies have published O-G "grandchild” programs. Some of these programs include: Wilson, Slingerland, Sonday, The Herman Method, Language!, Barton, Lindamood Individual Phoneme Sequencing (LiPS),  etc.  Each “grandchild” program has its own shtick or twist. For example, LiPS has an emphasis on articulatory feedback, Slingerland and Wilson were developed for use in school groups or classrooms, Sonday was developed for use with volunteers (or tutors with minimal background), Language! is now focused to address the needs of ELL students in classrooms, Barton is designed with video tutorials for parents. Lexercise is designed for online support in the use of the Orton-Gillingham Approach or any of its published "grandchildren."

These methods are also referred to as structured language methods because they all involve a highly structured and linguistically focused scope and sequence and teaching methods that are multisensory and explicit.  To use any structured language method effectively the provider must have a thorough knowledge of the structure of English print (orthography). Converging research suggests that a structured language approach is "best practice" for clients on the dyslexia spectrum. Although there is little or no research to suggest that one O-G "grandchild" program works any better than another, there is a lot of evidence that how much a clinician knows about the structure of English predicts their effectiveness.

Learning one "grandchild" program might be a good way to start since publishers often provide short "overview" workshops. However, an "overview" will probably not give you all you need to know about the structure of English print and how to teach it to people with processing problems.  Many clinicians struggle to implement structured language programs because they don't have deep enough knowledge of the print structure of English. 

There are advantages and disadvantages to learning O-G as an approach as compared to a learning it in the context of a published program:

• ADVANTAGE of learning O-G as an approach (i.e., not as a published "program"):  If you learn O-G as an approach you aren't tied to one set of materials or one scope & sequence. You can better use clinical reasoning to individualize and adapt it. Learning O-G as an approach stimulates you to think deeply about the methods.  See this link for some O-G Approach training courses we recommend.
• ADVANTAGE of learning O-G as applied to one, particular published "grandchild” program: You don't have to know as much or think as much.  You just follow the "program." You have one set of materials, and they are all in the publisher's "box."