Looking on the internet deeply has found these results:

say what you are thinking is the most popular phrase on the web.

say what's on your mind 1353,000 results on the web	say what you are thinking 1508,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
Okay, just say what's on your mind, Kyle. Julia, just say what's on your mind. The right time is when you as a man feel the need to say what's on your mind. Just say what's on your mind. Boys, when you become cops, have the courage to say what's on your mind. I have found that it's a real relief to say what's on your mind. If you talk, say what's on your mind... Julia, just say what's on your mind.	I didn't say what I was thinking. I too often say what I'm thinking. You're supposed to say, "What are you thinking, Wizard?" If you took this report, translated it into all the official languages and gave it to the men and women of Europe to read, they would be horrified; they would say, 'What are you thinking? Okay, let me just say what everyone's thinking. Just be honest, say what you're thinking. I'd say, "What are you thinking now?" Do not under any circumstances say what you're thinking.

say what's on your mind

1353,000 results on the web

say what you are thinking

1508,000 results on the web

More popular!

I didn't say what I was thinking.
I too often say what I'm thinking.
You're supposed to say, "What are you thinking, Wizard?"
If you took this report, translated it into all the official languages and gave it to the men and women of Europe to read, they would be horrified; they would say, 'What are you thinking?
Okay, let me just say what everyone's thinking.
Just be honest, say what you're thinking.
I'd say, "What are you thinking now?"
Do not under any circumstances say what you're thinking.