Yes, but the site's functionality is limited. Exchange-traded stock transactions can be entered during trading hours. CG online commissions are $2.95, and some ridiculous number for broker-assisted. No after hours trading. Fixed income can't even be quoted after hours. Officially you can't even transfer cash between accounts after hours, but sometimes it works.
Mutual funds can only be selected from 1-2 poorly-performing families, must be initiated by a broker, but lt least for free. Subsequent trades can be self-directed.