Maybe a bug.
I would expect the [(value)] binding on both of these mat-selects to work, but I can only get it to work on the first one.

this is the ts code

this is the result

So, only when not using the ngFor, does the [(value)] binding seem to work as expected.
https://stackblitz.com/edit/angular-1k7ykb?file=app%2Fselect-value-binding-example.html>
Material 6.4.7
Angular 6.1.7
Since you are trying to assign a object or variable as value of options, you'll need to add brackets around the "value" attribute, like [value]="o" will solve the problem.
Also consider using [(ngModel)] instead of [(value)] on the select.
See stackblitz: https://stackblitz.com/edit/angular-1k7ykb-cfmaq7
use [value]="o" or value="{{o}}" solve your problem.
@feeloor and @mungpara are correct. In your current example, the value for all the options is set to o. Closing as a non-issue.
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