Looking on the internet deeply has found these results:

proposal for is the most popular phrase on the web.

proposal of 1464,000 results on the web	proposal for 158,600,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
introduction re leaving age. More example sentences. His proposal to object to ... a proposal of something previously rejected; "they avoided a ... ( also proposal of marriage) → proposición f de matrimonio, propuesta f de ... ... is reviewing the proposal for the new restaurant. They put forth a proposal to sell the company. These problems have led to the proposal of a new law. Accepting his proposal of marriage might be setting her up for a fall, but ... Of course, a proposal of marriage was something that didn't come easy for him. 1.1 [ mass noun ] The action of proposing a plan or suggestion: the proposal of a flexible school	Parliament declined to give its consent to the proposal for a Council regulation. Commissioner rejected our proposal for a senior I've waited for your proposal for a long time. citiZens unit. Commission adoption of a proposal for prioritisation will follow. Check our proposal for your summer holidays 2018 in Tarragona. You are the one who tabled this proposal for a referendum. I fully support this proposal for establishing this Credit system.

proposal of

1464,000 results on the web

proposal for

158,600,000 results on the web

More popular!

introduction
re
leaving age. More example sentences. His proposal to object to ...
a proposal of something previously rejected; "they avoided a ... ( also proposal of marriage) → proposición f de matrimonio, propuesta f de ...
... is reviewing the proposal for the new restaurant. They put forth a proposal to sell the company. These problems have led to the proposal of a new law.
Accepting his proposal of marriage might be setting her up for a fall, but ... Of course, a proposal of marriage was something that didn't come easy for him.
1.1 [ mass noun ] The action of proposing a plan or suggestion: the proposal of a flexible school

Parliament declined to give its consent to the proposal for a Council regulation.
Commissioner rejected our proposal for a senior
I've waited for your proposal for a long time.
citiZens unit.
Commission adoption of a proposal for prioritisation will follow.
Check our proposal for your summer holidays 2018 in Tarragona.
You are the one who tabled this proposal for a referendum.
I fully support this proposal for establishing this Credit system.