Atmega8 USART transmitting wrong data
Most common error: You forgot the (default) Clock Div8 Fuse and your MCU runs on 1 MHz instead of 8 MHz. Try setting your COM Baudrate to 1200 Baud on the PC.

Another nitpick:

#define FOSC 8000000UL // Clock Speed
...
#define MYUBRR (((F_CPU / (BAUD * 16UL))) - 1)


Notice that you defined FOSC but then used F_CPU in your macro.