Even without any additional client software, Oracle Data Access Components (ODAC) is still a fairly sizable download, at over 60MB (closer to 130MB if you need to download both the 32-bit and 64-bit versions). For .NET applications, including those you build from scratch, Oracle provides another connectivity option: the Oracle Data Provider for .NET (ODP.NET). Starting with version 12.1, ODP.NET is available as a completely managed driver. This means the entire driver and supporting libraries are compiled to native .NET code and run entirely inside the CLR. The ODP.NET managed driver is included in the ODAC installation files, or you can download it separately from the Oracle website. ODP.NET is 1.9MB.
For more information about Oracle Data Access Components (ODAC), see "Connecting to an Oracle Database from SQL Server and Microsoft BI Tools."