40 yrs ago I saw the beginning of a movie on TV, a weekend afternoon, in which there is a portrait of prehistoric times that comes to life when you look at it. In one scene, a man throws a ball into the picture, a dog chases after the ball, and the dog's owner, a lady, chases after her dog by walking into this portrait as well. Then, then, someone starts painting over the portrait, and you see this lady turn circle back to try escaping before the last patch of scenery is covered over by this white paint. That's when I got dragged from the set. Does anyone know what movie that was? Thx

Sounds like something that might have been on the Twilight Zone or Outer Limits.

Thx for the idea. I checked the plots of all outer limits, and titles to all twilight zones of the era and didn't see it listed in either. Thx again though for the suggestion!

I think you're looking for a Night Gallery episode - The Painted Mirror... found some comments on it that seem to match what you've described:
...small dog going through the portal and the race to return to our world before the portal closes....... I was glad that the annoying yappy little dog got crunched by dinosaurs, that's for sure... ...Enjoyes this episode! She was pretty dumb to follow the dog, didn't it strike her as odd?...
(found discussion on the episode here:"The Painted Mirror" in Night Gallery Season 2 Forum... )

Wow, thank you! Just watched it. Funny though how it changed in my mind over the years. Thx again!

Great :)