USE abc

Create ROLE db_exec
go

GRANT EXECUTE TO db_exec
go

EXEC sp_addrolemember 'db_exec', 'abc_user'
go

use master
go

grant exec on sp_OACreate to abc_user
GO

SELECT *
FROM master.sys.database_permissions [dp]
JOIN master.sys.system_objects [so] ON dp.major_id = so.object_id
JOIN master.sys.sysusers [usr] ON
     usr.uid = dp.grantee_principal_id AND usr.name = 'abc_user'
WHERE permission_name = 'EXECUTE' AND so.name = 'sp_OACreate'

use master
grant exec on sp_OACreate to yourSecObject
grant exec on sp_OADestroy to yourSecObject  --Optional
grant exec on sp_OAMethod to yourSecObject

The EXECUTE permission was denied on the object 'xp_cmdshell', database 'mssqlsystemresource', schema 'sys'.
The EXECUTE permission was denied on the object 'sp_OACreate', database 'mssqlsystemresource', schema 'sys'.
The EXECUTE permission was denied on the object 'sp_OAMethod', database 'mssqlsystemresource', schema 'sys'.
The EXECUTE permission was denied on the object 'sp_OAMethod', database 'mssqlsystemresource', schema 'sys'.
The EXECUTE permission was denied on the object 'sp_OAMethod', database 'mssqlsystemresource', schema 'sys'.
The EXECUTE permission was denied on the object 'sp_OAGetProperty', database 'mssqlsystemresource', schema 'sys'.
The EXECUTE permission was denied on the object 'sp_OAGetProperty', database 'mssqlsystemresource', schema 'sys'.
The EXECUTE permission was denied on the object 'sp_OADestroy', database 'mssqlsystemresource', schema 'sys'.

EXEC sp_configure 'show advanced options', 1
GO
RECONFIGURE
GO
EXEC sp_configure 'xp_cmdshell', 1
GO
EXEC sp_configure 'show advanced options', 0
GO
RECONFIGURE
GO

use [master]
GO

GRANT EXECUTE ON [sys].[xp_cmdshell] TO [DOMAINusername];
GRANT EXECUTE ON [sys].[sp_OACreate] TO [DOMAINusername];
GRANT EXECUTE ON [sys].[sp_OADestroy] TO [DOMAINusername];
GRANT EXECUTE ON [sys].[sp_OAGetErrorInfo] TO [DOMAINusername];
GRANT EXECUTE ON [sys].[sp_OAGetProperty] TO [DOMAINusername];
GRANT EXECUTE ON [sys].[sp_OAMethod] TO [DOMAINusername];
GRANT EXECUTE ON [sys].[sp_OAStop] TO [DOMAINusername];
GRANT EXECUTE ON [sys].[sp_OASetProperty] TO [DOMAINusername];
GO

SELECT *
FROM master.sys.database_permissions [dp]
JOIN master.sys.system_objects [so] ON dp.major_id = so.object_id
JOIN master.sys.sysusers [usr] ON usr.uid = dp.grantee_principal_id AND usr.name = 'DOMAINusername'
WHERE permission_name = 'EXECUTE'
AND (so.name = 'xp_cmdshell'
  OR so.name = 'sp_OACreate'
  OR so.name = 'sp_OADestroy'
  OR so.name = 'sp_OAGetErrorInfo'
  OR so.name = 'sp_OAGetProperty'
  OR so.name = 'sp_OAMethod'
  OR so.name = 'sp_OAStop'
  OR so.name = 'sp_OASetProperty')