Retrieve all OptionSet values using OData in Dynamics CRM

You can use either the Web API or Organisation Service to retrieve The metadata and data models in Microsoft Dynamics CRM. Check out the sub articles of that one for specific examples and details.

Web API example Querying EntityMetadata attributes.

The following query will return only the PicklistAttributeMetadata attributes and will include the LogicalName as well as expanding the OptionSet and GlobalOptionSet collection-valued navigation properties.

GET [Organization URI]/api/data/v8.1/EntityDefinitions(70816501-edb9-4740-a16c-6a5efbc05d84)/Attributes/Microsoft.Dynamics.CRM.PicklistAttributeMetadata?$select=LogicalName&$expand=OptionSet,GlobalOptionSet