Players on Epic Games Store, PlayStation 4, Xbox One, Steam, and Nintendo Switch can randomly matchmake with or against each other in all Online Match types.
To enable Cross-Platform Play (it is enabled by default):
- In the Main Menu
- Select Options
- Select the Gameplay tab
- Check the Cross-Platform Play box
Click here for more info: Cross-Platform Support Now Live in Rocket League.
You can also play with friends on different platforms in Private Matches. Click here for instructions on How do I Create or Join a Private Match.