Possible Clues:

• Rocky Lane did his voice
• Four-footed TV star
• TV star who said 'Stop gabbin' and get me some oats!'
• Wilbur Post's pet
• Wilbur Post's 'pal'
• Wilbur was his owner
• Sitcom palomino
• Post horse?
• TV's neigh-sayer
• He conversed with Wilbur